Support streaming in parse_brat_file

bionlp_st_2019_bb.py

@@ -414,9 +414,11 @@ class bionlp_st_2019_bb(datasets.GeneratorBasedBuilder):
         ann_lines = []
         for suffix in annotation_file_suffixes:
             annotation_file = txt_file.with_suffix(suffix)
-            if annotation_file.exists():
+            try:
                 with annotation_file.open(encoding="utf8") as f:
                     ann_lines.extend(f.readlines())
+            except Exception:
+                continue
 
         example["text_bound_annotations"] = []
         example["events"] = []