code: def helper(p, q):
      if p is None and q is None:
          return True
      if p is not None or q is not None or q.val != p.val:
          return False
      return helper(p.left, q.right) and helper(p.right, q.left)
  
label_desc: Use image node_id 2 for calling a global function with example usage: helper(p, q) and returns: unknown, True, False