'Returns an instance of Model class by ID (and app, namespace).
This is the asynchronous version of Model._get_by_id().'

@classmethod
@utils.positional(3)
def _get_by_id_async(cls, id, parent=None, app=None, namespace=None, **ctx_options):

    key = Key(cls._get_kind(), id, parent=parent, app=app, namespace=namespace)
    return key.get_async(**ctx_options)
