code: def _validate_forbidden(self, forbidden_values, field, value):
          
          if isinstance(value, _str_type):
              if value in forbidden_values:
                  self._error(field, errors.FORBIDDEN_VALUE, value)
          elif isinstance(value, Sequence):
              forbidden = set(value) & set(forbidden_values)
              if forbidden:
                  self._error(field, errors.FORBIDDEN_VALUES, list(forbidden))
          elif isinstance(value, int):
              if value in forbidden_values:
                  self._error(field, errors.FORBIDDEN_VALUE, value)
docs: {'type': 'list'}