def METHOD_NAME(self, *args, **kwargs):
    if not hasattr(self, "log_class_type"):
        # for_concrete_model=False makes this also works for proxy models (that don't add any fields themselves
        # but just add rendering)
        self.log_class_type = ContentType.objects.get_for_model(
            self.__class__, for_concrete_model=False
        )
    super(LogEntry, self).METHOD_NAME(*args, **kwargs)