code: def test_extension_returns_none(client, extension_returns_none):
      """
      Ensures an extension that returns None is handled
      """
      extension_dir = extension_returns_none
  
      ext_mod_names = client.load_extensions(extension_dir)
  
      result = client.call_extension("my_extension")
      assert result is None
  
      # FIXME: much of this test could be in a fixture which ensures the extension
      # is unloaded from the server before returning
      for mod_name in ext_mod_names:
          client.unload_extension_module(mod_name)
  
imports: from collections.abc import Sequence
  from pathlib import Path
  import pytest
  from .None import data
label_desc: Use image node_id 14 for calling a global function with example usage: test_extension_returns_none(client, extension_returns_none) without return types