def serialize(self) -> dict:
        """ Serialize instance into json-friendly format. """
        return {
            'token': self.token,
            'sample_token': self.sample_token,
            'translation': self.translation,
            'size': self.size,
            'rotation': self.rotation,
            'velocity': self.velocity,
            'ego_translation': self.ego_translation,
            'num_pts': self.num_pts,
            'detection_name': self.detection_name,
            'detection_score': self.detection_score,
            'attribute_name': self.attribute_name,
            'visibility': self.visibility,
            'index': self.index

        }
 Serialize instance into json-friendly format. 
projects/mmdet3d_plugin/datasets/vad_custom_nuscenes_eval.py