def __getitem__(self, index):
        try:
            obj = self._storage[index]
        except KeyError:
            raise IndexError("Index %s out of range" % index)
        else:
            return obj()
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/util/_collections.py/WeakSequence.__getitem__/original