code: def test_get_session_info_on_invalid_session_id(self):
      assert (
          self.session_mgr.get_session_info("nonexistent_session")
          is None
      )
  
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 23 for calling the WebsocketSessionManagerTests obj's underlying member method code with example usage: obj.test_get_session_info_on_invalid_session_id() without return types