docs: def _get_roles_query(self, session, identifier):
          """
          :type identifier: string
          """
          return (session.query(Role).
                  join(role_membership_table, Role.pk_id == role_membership_table.c.role_id).
                  join(User, role_membership_table.c.user_id == User.pk_id).
                  filter(User.identifier == identifier))