code: def userId(self) -> Optional[str]:
      return "abc"
  
imports: import threading
  import time
  import unittest
  from typing import Optional
  from pyspark import InheritableThread, inheritable_thread_target
  from pyspark.sql.connect.client import ChannelBuilder
  from pyspark.sql.connect.session import SparkSession
  from pyspark.testing.connectutils import should_test_connect
label_desc: Use image node_id 1 for calling the CustomChannelBuilder obj's underlying member method code with example usage: obj.userId() and returns: str