code: def lum_contrast(clip, lum=0, contrast=0, contrast_threshold=127):
      """Luminosity-contrast correction of a clip."""
  
      def image_filter(im):
          im = 1.0 * im  # float conversion
          corrected = (
              im + lum + contrast * (im - float(contrast_threshold))
          )
          corrected[corrected < 0] = 0
          corrected[corrected > 255] = 255
          return corrected.astype("uint8")
  
      return clip.image_transform(image_filter)
  
label_desc: Use image node_id 1 for calling a global function with example usage: lum_contrast(clip, lum, contrast, contrast_threshold) and returns: clip, corrected