Replace assert of data/data_collator.py by ValueError (#14131)

* Replace assert of data_collator.py by ValueError

* Replace assert of data_collator.py by ValueError

src/transformers/data/data_collator.py

@@ -953,7 +953,8 @@ class DataCollatorForWholeWordMask(DataCollatorForLanguageModeling):
                 covered_indexes.add(index)
                 masked_lms.append(index)
 
-        assert len(covered_indexes) == len(masked_lms)
+        if len(covered_indexes) != len(masked_lms):
+            raise ValueError("Length of covered_indexes is not equal to length of masked_lms.")
         mask_labels = [1 if i in covered_indexes else 0 for i in range(len(input_tokens))]
         return mask_labels