code: def add(self, e):
      if e not in self._set:
          self._list.append(e)
          self._set.add(e)
  
imports: from __future__ import absolute_import
  import os
  import sys
  import re
  import io
  import codecs
  import shutil
  import tempfile
  from contextlib import contextmanager
label_desc: Use image node_id 4 for calling the OrderedSet obj's underlying member method code with example usage: obj.add(e) without return types