message: Fixes Github
  Changing example logs `acc` to `accuracy`
diff: @@ -671,7 +671,8 @@ class Callback(object):
  logs: Dict, metric results for this training epoch, and for the
  validation epoch if validation is performed. Validation result keys
  are prefixed with `val_`. For training epoch, the values of the
  - `Model`'s metrics are returned. Example : `{'loss': 0.2, 'acc': 0.7}`.
  + `Model`'s metrics are returned. Example : `{'loss': 0.2, 'accuracy':
  + 0.7}`.
  """
  @doc_controls.for_subclass_implementers
  