code: async def _wait_for_new(self, entity_type, entity_id):
          
          # if the entity is already in the model, just return it
          if entity_id in self.state._live_entity_map(entity_type):
              return self.state._live_entity_map(entity_type)[entity_id]
          return await self._wait(entity_type, entity_id, None)
docs: Wait for a new object to appear in the Model and return it.
  
          Waits for an object of type ``entity_type`` with id ``entity_id``
          to appear in the model.  This is similar to watching for the
          object using ``block_until``, but uses the watcher rather than
          polling.