How to Use embeddableDocumentStore.DocumentDatabase.StartBackup(...) Third Parameter

How to Use embeddableDocumentStore.DocumentDatabase.StartBackup(...) Third
Parameter

In RavenDB v2.5 a third parameter has been added to the StartBackup
method. How do you create/supply this third parameter? Everything I found
on the web only references two parameters.
embeddableDocumentStore.DocumentDatabase.StartBackup(string, bool,
**DatabaseDocument**)