Ensure that the Collection proxy has loaded all the items present in the Secret Service.
This affects the result of [method@Collection.get_items].
For collections returned from [method@Service.get_collections] the items will have already been loaded.
This method will return immediately and complete asynchronously.
| this |
the secret collection |
| cancellable |
optional cancellation object |
| callback |
called when the operation completes |
| user_data |
data to be passed to the callback |