def __init__(self,
                 url='sqlite:///:memory:',
                 equities=_default_equities,
                 **frames):
        self._url = url
        self._eng = None
        if equities is self._default_equities:
            equities = make_simple_equity_info(
                list(map(ord, 'ABC')),
                pd.Timestamp(0),
                pd.Timestamp('2015'),
            )

        frames['equities'] = equities
        self._frames = frames
        self._eng = None  # set in enter and exit