Initiates refresh on the this.
Finishing the method doesn't mean that the refresh is done, backend only notifies whether it started refreshing or not. Use
check_refresh_supported to check whether the backend supports this
method. The call is finished by refresh.end from the callback.
| this |
an Client |
| cancellable |
a Cancellable; can be |
| callback |
callback to call when a result is ready |
| user_data |
user data for the |