code: def validate_wrap(self, value):
          ''' Checks that ``value`` is an instance of ``DocumentField.type``.
              if it is, then validation on its fields has already been done and
              no further validation is needed.
          '''
          if not isinstance(value, self.type):
              self._fail_validation_type(value, self.typef validate_wrap(self, value):
          ''' Checks that ``value`` is an instance of ``DocumentField.type``.
              if it is, then validation on its fields has already been done and
              no further validation is needed.
          '''
          if not isinstance(value, self.type):
              self._fail_validation_type(value, self.type)
docs: Checks that ``value`` is an instance of ``DocumentField.type``.
              if it is, then validation on its fields has already been done and
              no further validation is needed.