def list_all_users(self):
        query = 'SELECT usename FROM pg_catalog.pg_user WHERE usename != %s'
        params = (self.user,)
        res = self.execute_sql(query, params)
        user_tuples = res['tuples']

        all_users_list = []
        for user_tuple in user_tuples:
            all_users_list.append(user_tuple[0])

        return all_users_list