public static extern unsafe void install_syncsession_callbacks(RefreshAccessTokenCallbackDelegate refresh_callback, SessionErrorCallback session_error_callback);
 public static extern unsafe void install_syncsession_callbacks(RefreshAccessTokenCallbackDelegate refresh_callback, SessionErrorCallback error_callback, SessionProgressCallback progress_callback, SessionWaitCallback wait_callback);
 public static extern void initialize_sync([MarshalAs(UnmanagedType.LPWStr)] string base_path, IntPtr base_path_leth, RefreshAccessTokenCallbackDelegate refresh_callback);