code: def _validate_operator_name(operator, supported_operators):
      
      if not isinstance(operator, six.text_type):
          raise TypeError(u'Expected operator as unicode string, got: {} {}'.format(
              type(operator).__name__, operator))
  
      if operator not in supported_operators:
          raise GraphQLCompilationError(u'Unrecognized operator: {}'.format(operator))
docs: Ensure the named operator is valid and supported.