code: def undef(self, tokens):
      id = tokens[0].value
      try:
          del self.macros[id]
      except LookupError:
          pass
  
imports: import sys
  import re
  import copy
  import time
  import os.path
label_desc: Use image node_id 16 for calling the Preprocessor obj's underlying member method code with example usage: obj.undef(tokens) without return types