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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 async def _wait_for_new(self, entity_type, entity_id):
 """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. """

        # 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)