code: def get_user_columns_list(self):
          
          ret_lst = list()
          for col_name in self.get_columns_list():
              if (not self.is_pk(col_name)) and (not self.is_fk(col_name)):
                  ret_lst.append(col_name)
          return ret_lst
docs: Returns all model's columns except pk or fk