def output_shape(self):
        """
        Returns:
            ShapeSpec: the output feature shape
        """
        o = self._output_size
        if isinstance(o, int):
            return ShapeSpec(channels=o)
        else:
            return ShapeSpec(channels=o[0], height=o[1], width=o[2])

        Returns:
            ShapeSpec: the output feature shape
        
video_chat_with_MOSS/models/grit_src/third_party/CenterNet2/detectron2/modeling/roi_heads/box_head.py