code: def ack2(M, N):
      if M == 0:
          return N + 1
      elif N == 0:
          return ack1(M - 1, 1)
      else:
          return ack1(M - 1, ack1(M, N - 1))
  
label_desc: Use image node_id 2 for calling a global function with example usage: ack2(M, N) and returns: unknown, ack1, ack1