code: def decode_string(s):
      """
      :type s: str
      :rtype: str
      """
      stack = []
      cur_num = 0
      cur_string = ""
      for c in s:
          if c == "[":
              stack.append((cur_string, cur_num))
              cur_string = ""
              cur_num = 0
          elif c == "]":
              prev_string, num = stack.pop()
              cur_string = prev_string + num * cur_string
          elif c.isdigit():
              cur_num = cur_num * 10 + int(c)
          else:
              cur_string += c
      return cur_string
  
label_desc: Use image node_id 1 for calling a global function with example usage: decode_string(s) and returns: cur_string