def extract_feature_3d(self, x: torch.Tensor) -> torch.Tensor:
        """ get the appearance feature of the image by F
        x: Bx3xHxW, normalized to 0~1
        """
        with torch.autocast(get_autocast_device(self.device_id), dtype=torch.float16) if self.cfg.flag_use_half_precision else nullcontext():
            feature_3d = self.appearance_feature_extractor(x)

        return feature_3d.float()
 get the appearance feature of the image by F
        x: Bx3xHxW, normalized to 0~1
        
liveportrait/live_portrait_wrapper.py