docstr: Regress the bbox for the predicted class. Used in Cascade R-CNN.
  
  Args:
      priors (Tensor): Priors from `rpn_head` or last stage
          `bbox_head`, has shape (num_proposals, 4).
      label (Tensor): Only used when `self.reg_class_agnostic`
          is False, has shape (num_proposals, ).
      bbox_pred (Tensor): Regression prediction of
          current stage `bbox_head`. When `self.reg_class_agnostic`
          is False, it has shape (n, num_classes * 4), otherwise
          it has shape (n, 4).
      img_meta (dict): Image meta info.
  
  Returns:
      Tensor: Regressed bboxes, the same shape as input rois.
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code: def regress(
      self, priors: Tensor, bbox_pred: Tensor, img_meta: dict
  ) -> Tensor:
      """Regress the bbox for the predicted class. Used in Cascade R-CNN.
  
      Args:
          priors (Tensor): Priors from `rpn_head` or last stage
              `bbox_head`, has shape (num_proposals, 4).
          label (Tensor): Only used when `self.reg_class_agnostic`
              is False, has shape (num_proposals, ).
          bbox_pred (Tensor): Regression prediction of
              current stage `bbox_head`. When `self.reg_class_agnostic`
              is False, it has shape (n, num_classes * 4), otherwise
              it has shape (n, 4).
          img_meta (dict): Image meta info.
  
      Returns:
          Tensor: Regressed bboxes, the same shape as input rois.
      """
      reg_dim = self.bbox_coder.encode_size
      assert bbox_pred.size()[1] == reg_dim
  
      max_shape = img_meta["img_shape"]
      regressed_bboxes = self.bbox_coder.decode(
          priors, bbox_pred, max_shape=max_shape
      )
      return regressed_bboxes
  
imports: import json
  from typing import List, Optional
  import torch
  from mmengine.config import ConfigDict
  from mmengine.structures import InstanceData
  from torch import Tensor
  from torch.nn import functional
  from mmdet.models.layers import multiclass_nms
  from mmdet.models.losses import accuracy
  from mmdet.models.roi_heads.bbox_heads import Shared2FCBBoxHead
  from mmdet.models.utils import empty_instances
  from mmdet.registry import MODELS
  from mmdet.structures.bbox import get_box_tensor, scale_boxes
  from mmdet.utils import ConfigType, InstanceList
label_desc: Use image node_id 7 for calling the DeticBBoxHead obj's underlying member method code with example usage: obj.regress(priors, bbox_pred, img_meta) and returns: regressed_bboxes