code: def save(self, *args, **kwargs):
          
          writer = None
          if 'writer' in kwargs.keys():
              writer = kwargs.pop('writer')
          else: writer = default_writer
          super().save(*args, **kwargs, writer=writer)
docs: Save animation into a movie file.
          
          [NOTE] If 'writer' is not specified, default writer defined in this module 
          will be used to generate the movie file.
  
          [TODO] Implement docstring inheritance.