def attempt_get(self, path, key):
        if len(self.contents) > 1:
            raise exc.InvalidRequestError(
                "Multiple classes found for path \"%s\" "
                "in the registry of this declarative "
                "base. Please use a fully module-qualified path." %
                (".".join(path + [key]))
            )
        else:
            ref = list(self.contents)[0]
            cls = ref()
            if cls is None:
                raise NameError(key)
            return cls
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/ext/declarative/clsregistry.py/_MultipleClassMarker.attempt_get/original