code: def RGB_to_Y(image):
      """Image has values from 0 to 1."""
  
      R = image[:, :, :, 0]
      G = image[:, :, :, 1]
      B = image[:, :, :, 2]
  
      Y = 16 + (65.738 * R) + 129.057 * G + 25.064 * B
      return Y / 255.0
  
label_desc: Use image node_id 2 for calling a global function with example usage: RGB_to_Y(image) and returns: unknown