code: def pad_if_smaller(img, size, fill=0):
      # 如果图像最小边长小于给定size，则用数值fill进行padding
      min_size = min(img.size)
      if min_size < size:
          ow, oh = img.size
          padh = size - oh if oh < size else 0
          padw = size - ow if ow < size else 0
          img = F.pad(img, (0, 0, padw, padh), fill=fill)
      return img
  
imports: import numpy
  import random
  import torch
  from torchvision import transforms
  from torchvision.transforms import functional
label_desc: Use image node_id 1 for calling a global function with example usage: pad_if_smaller(img, size, fill) and returns: img