code: def merge_two_list(l1, l2):
      ret = cur = Node(0)
      while l1 and l2:
          if l1.val < l2.val:
              cur.next = l1
              l1 = l1.next
          else:
              cur.next = l2
              l2 = l2.next
          cur = cur.next
      cur.next = l1 or l2
      return ret.next
  
label_desc: Use image node_id 1 for calling a global function with example usage: merge_two_list(l1, l2) and returns: ret