Revert back to list because you cannot have a free form dict as a feature

trec-cast-2019-multi-turn.py

@@ -128,12 +128,12 @@ class TrecCast2019MultiTurn(datasets.GeneratorBasedBuilder):
 
         if split == 'qrels':
             qrels_file = csv.reader(open(file), delimiter=" ")
-            qrels = defaultdict(dict)
+            qrels = defaultdict(list)
             for row in qrels_file:
                 qid = row[0]
                 docno = row[2]
                 rank = row[3]
-                qrels[qid][docno] = rank
+                qrels[qid].append({'docno': docno, 'rank': rank})
 
             for qid in qrels.keys():
                 yield qid, {'qid': qid, 'qrels': qrels[qid]}