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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def full_photos(self):
 """ Gets a list of photos using default options. :class:`list` of :class:`stravalib.model.ActivityPhoto` objects for this activity. """

        if self._photos is None:
            if self.total_photo_count > 0:
                self.assert_bind_client()
                self._photos = self.bind_client.get_activity_photos(self.id, only_instagram=False)
            else:
                self._photos = []
        return self._photos