code: def cost(z):
      """Cost function."""
      f0 = len(z[0][0]) / 10.0
      f1 = len(z[0][1]) / 10.0
      f2 = (z[1] - 21.3) / (243.9 - 21.3)
      return 0.1 + (f0 + f1) / 2 + 1.3 * f1 * f2**2
  
label_desc: Use image node_id 2 for calling a global function with example usage: cost(z) and returns: unknown