code: def postprocess(fg, alpha, img, bg, trans_info, writer, fg_estimate):
      """
      Postprocess for prediction results.
  
      Args:
          fg (Tensor): The foreground, value should be in [0, 1].
          alpha (Tensor): The alpha, value should be in [0, 1].
          img (Tensor): The original image, value should be in [0, 1].
          trans_info (list): A list of the shape transformations.
          writers (dict): A dict of VideoWriter instance.
          fg_estimate (bool): Whether to estimate foreground. It is invalid when fg is not None.
  
      """
      alpha = reverse_transform(alpha, trans_info)
      bg = F.interpolate(bg, size=alpha.shape[-2:], mode="bilinear")
      if fg is None:
          if fg_estimate:
              img = img.transpose((0, 2, 3, 1)).squeeze().numpy()
              alpha = alpha.squeeze().numpy()
              fg = estimate_foreground_ml(img, alpha)
              bg = bg.transpose((0, 2, 3, 1)).squeeze().numpy()
          else:
              fg = img
      else:
          fg = reverse_transform(fg, trans_info)
      if len(alpha.shape) == 2:
          alpha = alpha[:, :, None]
      new_img = alpha * fg + (1 - alpha) * bg
      writer.write(new_img)
  
file_path: PaddleSeg/Matting/ppmatting/core/bg_replace_video.py
imports: import os
  import math
  import time
  from collections.abc import Iterable
  import cv2
  import numpy
  import paddle
  import paddle.nn.functional
  from paddleseg import utils
  from paddleseg.core import infer
  from paddleseg.utils import logger, progbar, TimeAverager
  import ppmatting.transforms
  from ppmatting.utils import mkdir, estimate_foreground_ml, VideoReader, VideoWriter
label_desc: Use image node_id 3 for calling a global function with example usage: postprocess(fg, alpha, img, bg, trans_info, writer, fg_estimate) without return types