code: def _redundancy_routers_for_floatingip(
              self, context, router_id, redundancy_router_ids=None,
              ha_settings_db=None):
          
          if ha_settings_db is None:
              ha_settings_db = self._get_ha_settings_by_router_id(context,
                                                                  router_id)
          if ha_settings_db is None:
              return
  
          e_context = context.elevated()
          router_ids = []
          for r_id in (redundancy_router_ids or
                       self._get_redundancy_router_ids(e_context, router_id)):
              router_ids.append(r_id)
  
          return router_ids
docs: To be called in update_floatingip() to get the
              redundant router ids.