code: def refine_bboxes(proposal_bboxes, bbox_deltas):
      pred_bboxes = delta2bbox_v2(
          bbox_deltas.reshape([-1, 4]),
          proposal_bboxes.reshape([-1, 4]),
          delta_mean=[0.0, 0.0, 0.0, 0.0],
          delta_std=[0.5, 0.5, 1.0, 1.0],
          ctr_clip=None,
      )
      return pred_bboxes.reshape(proposal_bboxes.shape)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import copy
  import paddle
  from paddle import nn
  from ppdet.core.workspace import register
  from ppdet.modeling import initializer
  from .roi_extractor import RoIAlign
  from ..bbox_utils import delta2bbox_v2
  from ..cls_utils import _get_class_default_kwargs
  from ..layers import MultiHeadAttention
label_desc: Use image node_id 4 for calling the DIIHead obj's underlying member method code with example usage: obj.refine_bboxes(proposal_bboxes, bbox_deltas) and returns: pred_bboxes