File size: 21,856 Bytes
0fdcb79
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
import copy
import itertools
import time
import traceback
from collections import Counter
from functools import partial
import json
import os
import pickle
from typing import Optional, Sequence, Any

import ml_collections as mlc
import lightning as L
import torch
from torch.utils.data import RandomSampler

from dockformerpp.data.data_pipeline import parse_input_json
from dockformerpp.data import data_pipeline
from dockformerpp.utils.tensor_utils import dict_multimap
from dockformerpp.utils.tensor_utils import (
    tensor_tree_map,
)


class OpenFoldSingleDataset(torch.utils.data.Dataset):
    def __init__(self,
                 data_dir: str,
                 config: mlc.ConfigDict,
                 mode: str = "train",
                 ):
        """
            Args:
                data_dir:
                    A path to a directory containing mmCIF files (in train
                    mode) or FASTA files (in inference mode).
                config:
                    A dataset config object. See openfold.config
                mode:
                    "train", "val", or "predict"
        """
        super(OpenFoldSingleDataset, self).__init__()
        self.data_dir = data_dir

        self.config = config
        self.mode = mode

        valid_modes = ["train", "eval", "predict"]
        if mode not in valid_modes:
            raise ValueError(f'mode must be one of {valid_modes}')

        self._all_input_files = [i for i in os.listdir(data_dir) if i.endswith(".json")]
        if self.config.data_module.data_loaders.should_verify:
            self._all_input_files = [i for i in self._all_input_files if self._verify_json_input_file(i)]

        self.data_pipeline = data_pipeline.DataPipeline(config, mode)

    def _verify_json_input_file(self, file_name: str) -> bool:
        with open(os.path.join(self.data_dir, file_name), "r") as f:
            try:
                loaded = json.load(f)
                for i in ["input_structure"]:
                    if i not in loaded:
                        return False
                if self.mode != "predict":
                    for i in ["gt_structure", "resolution"]:
                        if i not in loaded:
                            return False
            except json.JSONDecodeError:
                return False
        return True

    def get_metadata_for_idx(self, idx: int) -> dict:
        input_path = os.path.join(self.data_dir, self._all_input_files[idx])
        input_data = json.load(open(input_path, "r"))
        metadata = {
            "resolution": input_data.get("resolution", 99.0),
            "input_path": input_path,
            "input_name": os.path.basename(input_path).split(".json")[0],
        }
        return metadata

    def __getitem__(self, idx):
        return parse_input_json(
            input_path=os.path.join(self.data_dir, self._all_input_files[idx]),
            mode=self.mode,
            config=self.config,
            data_pipeline=self.data_pipeline,
            data_dir=os.path.dirname(self.data_dir),
            idx=idx,
        )

    def __len__(self):
        return len(self._all_input_files)


def resolution_filter(resolution: int, max_resolution: float) -> bool:
    """Check that the resolution is <= max_resolution permitted"""
    return resolution is not None and resolution <= max_resolution


def all_seq_len_filter(seqs: list, minimum_number_of_residues: int) -> bool:
    """Check if the total combined sequence lengths are >= minimum_numer_of_residues"""
    total_len = sum([len(i) for i in seqs])
    return total_len >= minimum_number_of_residues


class OpenFoldDataset(torch.utils.data.Dataset):
    """
        Implements the stochastic filters applied during AlphaFold's training.
        Because samples are selected from constituent datasets randomly, the
        length of an OpenFoldFilteredDataset is arbitrary. Samples are selected
        and filtered once at initialization.
    """

    def __init__(self,
                 datasets: Sequence[OpenFoldSingleDataset],
                 probabilities: Sequence[float],
                 epoch_len: int,
                 generator: torch.Generator = None,
                 _roll_at_init: bool = True,
                 ):
        self.datasets = datasets
        self.probabilities = probabilities
        self.epoch_len = epoch_len
        self.generator = generator

        self._samples = [self.looped_samples(i) for i in range(len(self.datasets))]
        if _roll_at_init:
            self.reroll()

    @staticmethod
    def deterministic_train_filter(
        cache_entry: Any,
        max_resolution: float = 9.,
        max_single_aa_prop: float = 0.8,
        *args, **kwargs
    ) -> bool:
        # Hard filters
        resolution = cache_entry["resolution"]

        return all([
            resolution_filter(resolution=resolution,
                              max_resolution=max_resolution)
        ])

    @staticmethod
    def get_stochastic_train_filter_prob(
        cache_entry: Any,
        *args, **kwargs
    ) -> float:
        # Stochastic filters
        probabilities = []

        cluster_size = cache_entry.get("cluster_size", None)
        if cluster_size is not None and cluster_size > 0:
            probabilities.append(1 / cluster_size)

        # Risk of underflow here?
        out = 1
        for p in probabilities:
            out *= p

        return out

    def looped_shuffled_dataset_idx(self, dataset_len):
        while True:
            # Uniformly shuffle each dataset's indices
            weights = [1. for _ in range(dataset_len)]
            shuf = torch.multinomial(
                torch.tensor(weights),
                num_samples=dataset_len,
                replacement=False,
                generator=self.generator,
            )
            for idx in shuf:
                yield idx

    def looped_samples(self, dataset_idx):
        max_cache_len = int(self.epoch_len * self.probabilities[dataset_idx])
        dataset = self.datasets[dataset_idx]
        idx_iter = self.looped_shuffled_dataset_idx(len(dataset))
        while True:
            weights = []
            idx = []
            for _ in range(max_cache_len):
                candidate_idx = next(idx_iter)
                # chain_id = dataset.idx_to_chain_id(candidate_idx)
                # chain_data_cache_entry = chain_data_cache[chain_id]
                # data_entry = dataset[candidate_idx.item()]
                entry_metadata_for_filter = dataset.get_metadata_for_idx(candidate_idx.item())
                if not self.deterministic_train_filter(entry_metadata_for_filter):
                    continue

                p = self.get_stochastic_train_filter_prob(
                    entry_metadata_for_filter,
                )
                weights.append([1. - p, p])
                idx.append(candidate_idx)

            samples = torch.multinomial(
                torch.tensor(weights),
                num_samples=1,
                generator=self.generator,
            )
            samples = samples.squeeze()

            cache = [i for i, s in zip(idx, samples) if s]

            for datapoint_idx in cache:
                yield datapoint_idx

    def __getitem__(self, idx):
        dataset_idx, datapoint_idx = self.datapoints[idx]
        return self.datasets[dataset_idx][datapoint_idx]

    def __len__(self):
        return self.epoch_len

    def reroll(self):
        # TODO bshor: I have removed support for filters (currently done in preprocess) and to weighting clusters
        # now it is much faster, because it doesn't call looped_samples
        dataset_choices = torch.multinomial(
            torch.tensor(self.probabilities),
            num_samples=self.epoch_len,
            replacement=True,
            generator=self.generator,
        )
        self.datapoints = []
        counter_datasets = Counter(dataset_choices.tolist())
        for dataset_idx, num_samples in counter_datasets.items():
            dataset = self.datasets[dataset_idx]
            sample_choices = torch.randint(0, len(dataset), (num_samples,), generator=self.generator)
            for datapoint_idx in sample_choices:
                self.datapoints.append((dataset_idx, datapoint_idx))


class OpenFoldBatchCollator:
    def __call__(self, prots):
        stack_fn = partial(torch.stack, dim=0)
        return dict_multimap(stack_fn, prots)


class OpenFoldDataLoader(torch.utils.data.DataLoader):
    def __init__(self, *args, config, stage="train", generator=None, **kwargs):
        super().__init__(*args, **kwargs)
        self.config = config
        self.stage = stage
        self.generator = generator
        self._prep_batch_properties_probs()

    def _prep_batch_properties_probs(self):
        keyed_probs = []
        stage_cfg = self.config[self.stage]

        max_iters = self.config.common.max_recycling_iters

        if stage_cfg.uniform_recycling:
            recycling_probs = [
                1. / (max_iters + 1) for _ in range(max_iters + 1)
            ]
        else:
            recycling_probs = [
                0. for _ in range(max_iters + 1)
            ]
            recycling_probs[-1] = 1.

        keyed_probs.append(
            ("no_recycling_iters", recycling_probs)
        )

        keys, probs = zip(*keyed_probs)
        max_len = max([len(p) for p in probs])
        padding = [[0.] * (max_len - len(p)) for p in probs]

        self.prop_keys = keys
        self.prop_probs_tensor = torch.tensor(
            [p + pad for p, pad in zip(probs, padding)],
            dtype=torch.float32,
        )

    def _add_batch_properties(self, batch):
        # gt_features = batch.pop('gt_features', None)
        samples = torch.multinomial(
            self.prop_probs_tensor,
            num_samples=1,  # 1 per row
            replacement=True,
            generator=self.generator
        )

        aatype = batch["aatype"]
        batch_dims = aatype.shape[:-2]
        recycling_dim = aatype.shape[-1]
        no_recycling = recycling_dim
        for i, key in enumerate(self.prop_keys):
            sample = int(samples[i][0])
            sample_tensor = torch.tensor(
                sample,
                device=aatype.device,
                requires_grad=False
            )
            orig_shape = sample_tensor.shape
            sample_tensor = sample_tensor.view(
                (1,) * len(batch_dims) + sample_tensor.shape + (1,)
            )
            sample_tensor = sample_tensor.expand(
                batch_dims + orig_shape + (recycling_dim,)
            )
            batch[key] = sample_tensor

            if key == "no_recycling_iters":
                no_recycling = sample

        resample_recycling = lambda t: t[..., :no_recycling + 1]
        batch = tensor_tree_map(resample_recycling, batch)
        # batch['gt_features'] = gt_features

        return batch

    def __iter__(self):
        it = super().__iter__()

        def _batch_prop_gen(iterator):
            for batch in iterator:
                yield self._add_batch_properties(batch)

        return _batch_prop_gen(it)


class OpenFoldDataModule(L.LightningDataModule):
    def __init__(self,
                 config: mlc.ConfigDict,
                 train_data_dir: Optional[str] = None,
                 val_data_dir: Optional[str] = None,
                 predict_data_dir: Optional[str] = None,
                 batch_seed: Optional[int] = None,
                 train_epoch_len: int = 50000,
                 **kwargs
                 ):
        super(OpenFoldDataModule, self).__init__()

        self.config = config
        self.train_data_dir = train_data_dir
        self.val_data_dir = val_data_dir
        self.predict_data_dir = predict_data_dir
        self.batch_seed = batch_seed
        self.train_epoch_len = train_epoch_len

        if self.train_data_dir is None and self.predict_data_dir is None:
            raise ValueError(
                'At least one of train_data_dir or predict_data_dir must be '
                'specified'
            )

        self.training_mode = self.train_data_dir is not None

        # if not self.training_mode and predict_alignment_dir is None:
        #     raise ValueError(
        #         'In inference mode, predict_alignment_dir must be specified'
        #     )
        # elif val_data_dir is not None and val_alignment_dir is None:
        #     raise ValueError(
        #         'If val_data_dir is specified, val_alignment_dir must '
        #         'be specified as well'
        #     )

    def setup(self, stage):
        # Most of the arguments are the same for the three datasets 
        dataset_gen = partial(OpenFoldSingleDataset,
                              config=self.config)

        if self.training_mode:
            train_dataset = dataset_gen(
                data_dir=self.train_data_dir,
                mode="train",
            )

            datasets = [train_dataset]
            probabilities = [1.]

            generator = None
            if self.batch_seed is not None:
                generator = torch.Generator()
                generator = generator.manual_seed(self.batch_seed + 1)

            self.train_dataset = OpenFoldDataset(
                datasets=datasets,
                probabilities=probabilities,
                epoch_len=self.train_epoch_len,
                generator=generator,
                _roll_at_init=False,
            )

            if self.val_data_dir is not None:
                self.eval_dataset = dataset_gen(
                    data_dir=self.val_data_dir,
                    mode="eval",
                )
            else:
                self.eval_dataset = None
        else:
            self.predict_dataset = dataset_gen(
                data_dir=self.predict_data_dir,
                mode="predict",
            )

    def _gen_dataloader(self, stage):
        generator = None
        if self.batch_seed is not None:
            generator = torch.Generator()
            generator = generator.manual_seed(self.batch_seed)

        if stage == "train":
            dataset = self.train_dataset
            # Filter the dataset, if necessary
            dataset.reroll()
        elif stage == "eval":
            dataset = self.eval_dataset
        elif stage == "predict":
            dataset = self.predict_dataset
        else:
            raise ValueError("Invalid stage")

        batch_collator = OpenFoldBatchCollator()

        dl = OpenFoldDataLoader(
            dataset,
            config=self.config,
            stage=stage,
            generator=generator,
            batch_size=self.config.data_module.data_loaders.batch_size,
            # num_workers=self.config.data_module.data_loaders.num_workers,
            num_workers=0, # TODO bshor: solve generator pickling issue and then bring back num_workers, or just remove generator
            collate_fn=batch_collator,
        )

        return dl

    def train_dataloader(self):
        return self._gen_dataloader("train")

    def val_dataloader(self):
        if self.eval_dataset is not None:
            return self._gen_dataloader("eval")
        return None

    def predict_dataloader(self):
        return self._gen_dataloader("predict")


class DummyDataset(torch.utils.data.Dataset):
    def __init__(self, batch_path):
        with open(batch_path, "rb") as f:
            self.batch = pickle.load(f)

    def __getitem__(self, idx):
        return copy.deepcopy(self.batch)

    def __len__(self):
        return 1000


class DummyDataLoader(L.LightningDataModule):
    def __init__(self, batch_path):
        super().__init__()
        self.dataset = DummyDataset(batch_path)

    def train_dataloader(self):
        return torch.utils.data.DataLoader(self.dataset)


class DockFormerSimpleDataset(torch.utils.data.Dataset):
    def __init__(self, clusters_json: str, config: mlc.ConfigDict, mode: str = "train"):
        clusters = json.load(open(clusters_json, "r"))
        self.config = config
        self.mode = mode
        self._data_dir = os.path.dirname(clusters_json)
        print("Data dir", self._data_dir)
        self._clusters = clusters
        self._all_input_files = sum(clusters.values(), [])
        self.data_pipeline = data_pipeline.DataPipeline(config, mode)

    def __getitem__(self, idx):
        return parse_input_json(
            input_path=os.path.join(self._data_dir, self._all_input_files[idx]),
            mode=self.mode,
            config=self.config,
            data_pipeline=self.data_pipeline,
            data_dir=self._data_dir,
            idx=idx,
        )

    def __len__(self):
        return len(self._all_input_files)


class DockFormerClusteredDataset(torch.utils.data.Dataset):
    def __init__(self, clusters_json: str, config: mlc.ConfigDict, mode: str = "train", generator=None):
        clusters = json.load(open(clusters_json, "r"))
        self.config = config
        self.mode = mode
        self._data_dir = os.path.dirname(clusters_json)
        self._clusters = list(clusters.values())
        self.data_pipeline = data_pipeline.DataPipeline(config, mode)
        self._generator = generator

    def __getitem__(self, idx):
        try:
            cluster = self._clusters[idx]
            # choose random from cluster
            input_file = cluster[torch.randint(0, len(cluster), (1,), generator=self._generator).item()]

            return parse_input_json(
                input_path=os.path.join(self._data_dir, input_file),
                mode=self.mode,
                config=self.config,
                data_pipeline=self.data_pipeline,
                data_dir=self._data_dir,
                idx=idx,
            )
        except Exception as e:
            print("ERROR in loading", e)
            traceback.print_exc()
            return parse_input_json(
                input_path=os.path.join(self._data_dir, self._clusters[0][0]),
                mode=self.mode,
                config=self.config,
                data_pipeline=self.data_pipeline,
                data_dir=self._data_dir,
                idx=idx,
            )


    def __len__(self):
        return len(self._clusters)


class DockFormerDataLoader(torch.utils.data.DataLoader):
    def __init__(self, *args, config, stage="train", generator=None, **kwargs):
        super().__init__(*args, **kwargs)
        self.config = config
        self.stage = stage
        # self.generator = generator

    def _add_batch_properties(self, batch):
        if self.config[self.stage].uniform_recycling:
            aatype = batch["aatype"]
            max_recycling_dim = aatype.shape[-1]

            # num_recycles = torch.randint(0, max_recycling_dim, (1,), generator=self.generator)
            num_recycles = torch.randint(0, max_recycling_dim, (1,)).item()

            resample_recycling = lambda t: t[..., :num_recycles + 1]
            batch = tensor_tree_map(resample_recycling, batch)

        return batch

    def __iter__(self):
        it = super().__iter__()

        def _batch_prop_gen(iterator):
            for batch in iterator:
                yield self._add_batch_properties(batch)

        return _batch_prop_gen(it)


class DockFormerDataModule(L.LightningDataModule):
    def __init__(self,
                 config: mlc.ConfigDict,
                 train_data_file: Optional[str] = None,
                 val_data_file: Optional[str] = None,
                 batch_seed: Optional[int] = None,
                 **kwargs
                 ):
        super(DockFormerDataModule, self).__init__()

        self.config = config
        self.train_data_file = train_data_file
        self.val_data_file = val_data_file
        self.batch_seed = batch_seed

        assert self.train_data_file is not None, "train_data_file must be specified"
        assert self.val_data_file is not None, "val_data_file must be specified"

        self.train_dataset = None
        self.val_dataset = None

    def setup(self, stage):
        generator = None
        if self.batch_seed is not None:
            generator = torch.Generator()
            generator = generator.manual_seed(self.batch_seed + 1)

        self.train_dataset = DockFormerClusteredDataset(
            clusters_json=self.train_data_file,
            config=self.config,
            mode="train",
            generator=generator,
        )

        self.val_dataset = DockFormerSimpleDataset(
            clusters_json=self.val_data_file,
            config=self.config,
            mode="eval",
        )

    def _gen_dataloader(self, stage):
        generator = None
        if self.batch_seed is not None:
            generator = torch.Generator()
            generator = generator.manual_seed(self.batch_seed)

        should_shuffle = stage == "train"
        if stage == "train":
            dataset = self.train_dataset
        elif stage == "eval":
            dataset = self.val_dataset
        else:
            raise ValueError("Invalid stage")

        batch_collator = OpenFoldBatchCollator()

        dl = DockFormerDataLoader(
            dataset,
            config=self.config,
            stage=stage,
            # generator=generator,
            batch_size=self.config.data_module.data_loaders.batch_size,
            # num_workers=self.config.data_module.data_loaders.num_workers,
            num_workers=0, # TODO bshor: solve generator pickling issue and then bring back num_workers, or just remove generator
            collate_fn=batch_collator,
            shuffle=should_shuffle,
        )

        return dl

    def train_dataloader(self):
        return self._gen_dataloader("train")

    def val_dataloader(self):
        if self.val_dataset is not None:
            return self._gen_dataloader("eval")
        return None