code: def test_list_all(self):
      self.assertEqual(channels.list_all(), [])
      created = set()
      for _ in range(3):
          ch = channels.create()
          created.add(ch)
      after = set(channels.list_all())
      self.assertEqual(after, created)
  
imports: import threading
  from textwrap import dedent
  import unittest
  import time
  from test.support import import_helper
  from test.support import interpreters
  from test.support.interpreters import channels
  from .utils import _run_output, TestBase
label_desc: Use image node_id 2 for calling the TestChannels obj's underlying member method code with example usage: obj.test_list_all() without return types