Lookup a password in the secret service.
The variable argument list should contain pairs of a) The attribute name as a null-terminated string, followed by b) attribute value,
either a character string, an int number, or a gboolean value, as defined in the password schema. The list of attributes
should be terminated with a null.
If no secret is found then null is returned.
This method will return immediately and complete asynchronously.
| schema |
the schema for the attributes |
| cancellable |
optional cancellation object |
| ... |
the attribute keys and values, terminated with null |
| callback |
called when the operation completes |
| user_data |
data to be passed to the callback |