code: def color_normalize(src, mean, std=None):
      
      if mean is not None:
          src -= mean
      if std is not None:
          src /= std
      return src
docs: Normalize src with mean and std.
  
      Parameters
      ----------
      src : NDArray
          Input image
      mean : NDArray
          RGB mean to be subtracted
      std : NDArray
          RGB standard deviation to be divided
  
      Returns
      -------
      NDArray
          An `NDArray` containing the normalized image.