code: def test_list_sessions(self):
      session_ids = []
      for _ in range(3):
          session_ids.append(self.connect_session())
  
      self.session_mgr.disconnect_session(session_ids[1])
  
      # Sanity check.
      assert self.session_mgr.is_active_session(session_ids[0])
      assert not self.session_mgr.is_active_session(session_ids[1])
      assert self.session_mgr.is_active_session(session_ids[2])
  
      assert {
          s.session.id for s in self.session_mgr.list_sessions()
      } == set(session_ids)
  
imports: import unittest
  from unittest.mock import MagicMock, patch
  import pytest
  from streamlit.runtime.script_data import ScriptData
  from streamlit.runtime.session_manager import SessionStorage
  from streamlit.runtime.websocket_session_manager import WebsocketSessionManager
label_desc: Use image node_id 24 for calling the WebsocketSessionManagerTests obj's underlying member method code with example usage: obj.test_list_sessions() without return types