code: def serialize_model(self, model, field_dict=None):
          
          response = self._serialize_model_helper(model, field_dict=field_dict)
          return make_json_safe(response)
docs: Takes a model and serializes the fields provided into
          a dictionary.
  
          :param Model model: The Sqlalchemy model instance to serialize
          :param dict field_dict: The dictionary of fields to return.
          :return: The serialized model.
          :rtype: dict