message: Update grouping.py
  Fix pylint issues.
diff: @@ -169,8 +169,8 @@ def bucket_by_sequence_length(element_length_func,
  There is also a possibility to pad the dataset till the bucket boundary.
  You can also provide which value to be used while padding the data.
  - Below example uses `-1` as padding and it also shows the input data being bucketizied to two buckets
  - "[0,3], [4,6]"
  + Below example uses `-1` as padding and it also shows the input data
  + being bucketizied to two buckets "[0,3], [4,6]".
  >>> elements = [
  ... [0], [1, 2, 3, 4], [5, 6, 7],
  @@ -196,10 +196,11 @@ def bucket_by_sequence_length(element_length_func,
  [[21 22 -1]]
  [[13 14 15 16 19 20]]
  - When using `pad_to_bucket_boundary` option, it can be seen that it is not always possible
  - to maintain the bucket batch size.
  - You can drop the batches that do not maintain the bucket batch size by using the option `drop_remainder`.
  - Using the same input data as in the above example you get the following result.
  + When using `pad_to_bucket_boundary` option, it can be seen that it is
  + not always possible to maintain the bucket batch size.
  + You can drop the batches that do not maintain the bucket batch size by
  + using the option `drop_remainder`. Using the same input data as in the
  + above example you get the following result.
  >>> elements = [
  ... [0], [1, 2, 3, 4], [5, 6, 7],
  