Update files from the datasets library (from 1.6.1)

Release notes: https://github.com/huggingface/datasets/releases/tag/1.6.1

cord19.py

@@ -147,7 +147,7 @@ class Cord19(datasets.GeneratorBasedBuilder):
         ]
 
     def _generate_examples(self, filepath, split):
-        """ Yields examples. """
+        """Yields examples."""
 
         metadata_filepath = filepath["metadata"]