code: def start_tree(self, tree, filename):
      super(FixExitfunc, self).start_tree(tree, filename)
      self.sys_import = None
  
imports: from lib2to3 import pytree, fixer_base
  from lib2to3.fixer_util import Name, Attr, Call, Comma, Newline, syms
label_desc: Use image node_id 2 for calling the FixExitfunc obj's underlying member method code with example usage: obj.start_tree(tree, filename) without return types