Reformat source code with black.

This is the result of:

    $ black --line-length 119 examples templates transformers utils hubconf.py setup.py

There's a lot of fairly long lines in the project. As a consequence, I'm
picking the longest widely accepted line length, 119 characters.

This is also Thomas' preference, because it allows for explicit variable
names, to make the code easier to understand.

examples/summarization/utils_summarization.py

@@ -68,9 +68,7 @@ def process_story(raw_story):
     Raises:
         IndexError: If the stoy is empty or contains no highlights.
     """
-    nonempty_lines = list(
-        filter(lambda x: len(x) != 0, [line.strip() for line in raw_story.split("\n")])
-    )
+    nonempty_lines = list(filter(lambda x: len(x) != 0, [line.strip() for line in raw_story.split("\n")]))
 
     # for some unknown reason some lines miss a period, add it
     nonempty_lines = [_add_missing_period(line) for line in nonempty_lines]
@@ -135,13 +133,9 @@ def encode_for_summarization(story_lines, summary_lines, tokenizer):
     sentences.
     """
     story_lines_token_ids = [tokenizer.encode(line) for line in story_lines]
-    story_token_ids = [
-        token for sentence in story_lines_token_ids for token in sentence
-    ]
+    story_token_ids = [token for sentence in story_lines_token_ids for token in sentence]
     summary_lines_token_ids = [tokenizer.encode(line) for line in summary_lines]
-    summary_token_ids = [
-        token for sentence in summary_lines_token_ids for token in sentence
-    ]
+    summary_token_ids = [token for sentence in summary_lines_token_ids for token in sentence]
 
     return story_token_ids, summary_token_ids