def nonempty(self, threshold: float = 0.0) -> torch.Tensor:
        """
        Find boxes that are non-empty.
        A box is considered empty, if either of its side is no larger than threshold.

        Returns:
            Tensor: a binary vector which represents
            whether each box is empty (False) or non-empty (True).
        """
        box = self.tensor
        widths = box[:, 2]
        heights = box[:, 3]
        keep = (widths > threshold) & (heights > threshold)
        return keep

        Find boxes that are non-empty.
        A box is considered empty, if either of its side is no larger than threshold.

        Returns:
            Tensor: a binary vector which represents
            whether each box is empty (False) or non-empty (True).
        
video_chat_text/video_chat_with_ChatGPT/models/grit_src/third_party/CenterNet2/detectron2/structures/rotated_boxes.py