code: def __call__(self, pred_label, *args, **kwargs):
      metric = {}
      images_sr = pred_label["sr_img"]
      images_hr = pred_label["hr_img"]
      psnr = self.calculate_psnr(images_sr, images_hr)
      ssim = self.calculate_ssim(images_sr, images_hr)
      self.psnr_result.append(psnr)
      self.ssim_result.append(ssim)
  
imports: from math import exp
  import paddle
  import paddle.nn.functional
  import paddle.nn
  import string
label_desc: Use image node_id 5 for calling the SRMetric obj's underlying member method code with example usage: obj.__call__(pred_label) without return types