code: def _converter(self, value):
          
          if type(value) is not self.related_model_cls.Collection:
              value = self.related_model_cls.Collection([
                  self._get_model_instance(self.related_model_cls, item)
                  for item in value])
          return value
docs: Convert raw input value of the field.
  
          :param object value:
          :rtype object: