Function ostree::checksum_file_async

pub fn checksum_file_async<P: IsA<File>, Q: IsA<Cancellable>, R: FnOnce(Result<Checksum, Box<dyn Error>>) + Send + 'static>(
    f: &P, 
    objtype: ObjectType, 
    io_priority: i32, 
    cancellable: Option<&Q>, 
    callback: R
)