docs: def _fetch_arguments(handler, method):
      """Get the arguments depending on the type of HTTP method."""
  
      if method.__name__ == 'get':
          arguments = {}
          for key, value in six.iteritems(handler.request.arguments):
              # Tornado supports comma-separated lists of values in
              # parameters. We're undoing that here, and if a list
              # is expected the _validate method can handle it.
              if isinstance(value, list):
                  arguments[key] = ','.join(value)
              else:
                  arguments[key] = value
      else:  # post, put, patch, delete?
          arguments = handler.get_post_arguments()
  
      return arguments