Runs a prompt and performs the prompting.
Returns true if the prompt was completed and not dismissed.
If window_id is non-null then it is used as an XWindow id on Linux. The API expects this id to be converted to a string
using the `%d` printf format. The Secret Service can make its prompt transient for the window with this id. In some Secret Service
implementations this is not possible, so the behavior depending on this should degrade gracefully.
This method will return immediately and complete asynchronously.
| this |
a prompt |
| window_id |
string form of XWindow id for parent window to be transient for |
| return_type |
the variant type of the prompt result |
| cancellable |
optional cancellation object |
| callback |
called when the operation completes |
| user_data |
data to be passed to the callback |