Returns all model's columns except pk or fk

def get_user_columns_list(self):
        """
            Returns all model's columns except pk or fk
        """
        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