docs: def _get_context(argspec, kwargs):
      """Prepare a context for the serialization.
  
      :param argspec: The argspec of the serialization function.
      :param kwargs: Dict with context
      :return: Keywords arguments that function can accept.
      """
      if argspec.keywords is not None:
          return kwargs
      return dict((arg, kwargs[arg]) for arg in argspec.args if arg in kwargs)