@callback
def _async_track_unavailable(self):
    if self._remove_unavailability_tracker:
        self._remove_unavailability_tracker()
    self._remove_unavailability_tracker = async_track_point_in_utc_time(self.hass, self._async_set_unavailable, (utcnow() + TIME_TILL_UNAVAILABLE))
    if (not self._is_available):
        self._is_available = True
        return True
    return False
@callback
def _async_track_unavailable(self):
    if self._remove_unavailability_tracker:
        self._remove_unavailability_tracker()
    self._remove_unavailability_tracker = async_track_point_in_utc_time(self.hass, self._async_set_unavailable, (utcnow() + TIME_TILL_UNAVAILABLE))
    if (not self._is_available):
        self._is_available = True
        return True
    return False