def __init__(self, name, host='127.0.0.1', port=27017):
        self.name = name
        self.host = host
        self.port = port
def _assert_type(self, value, t, id, expected):
        if not isinstance(value, t):
            raise TransactionError(_('Unexpected type of "{id}", {exp} expected.').format(id=id, exp=expected))