Check whether or not the user is logged in.

def _is_logged_in(self):
        """ Check whether or not the user is logged in. """
        # if the user has not logged in in 24 hours, relogin
        if not self._http._has_session() or datetime.utcnow() >= self._lastlogin + timedelta(hours=24):
            return self._login()
        else:
            return {}