docs: def get_api_client():
      """Gets the reference to the API cient (singleton)."""
      with _api_lock:
          global _api_client
          if not _api_client:
              conf_file = os.path.join(os.environ.get("HOME"),
                                       ".python-grid5000.yaml")
              _api_client = Client.from_yaml(conf_file)
  
          return _api_client