code: def grad_cam(feat, grad):
      """
  
      Args:
          feat:  CxHxW
          grad:  CxHxW
  
      Returns:
             cam: HxW
      """
      exp = (feat * grad.mean((1, 2), keepdims=True)).mean(axis=0)
      exp = np.maximum(-exp, 0)
      return exp
  
file_path: PaddleDetection/ppdet/utils/cam_utils.py
imports: import numpy
  import cv2
  import os
  import sys
  import glob
  from ppdet.utils.logger import setup_logger
  import copy
  import paddle
  from ppdet.engine import Trainer
label_desc: Use image node_id 3 for calling a global function with example usage: grad_cam(feat, grad) and returns: exp