@property
def quan(self):
    if (self._quan is not None):
        return self._quan
    self._quan = functools.partial(YTQuantity, registry=self.unit_registry)
    return self._quan
@property
def quan(self):
    if (self._quan is not None):
        return self._quan
    self._quan = functools.partial(YTQuantity, registry=self.unit_registry)
    return self._quan