Type Alias WriteTransform 

pub type WriteTransform = Arc<dyn Fn(&Message) -> Option<String> + Send + Sync + 'static>;

A function that decides what (if anything) to persist for a single message. Returning None skips the message.

Returning Some("") is treated identically to None: empty payloads are never written to the archive.

Aliased Type

pub struct WriteTransform { /* private fields */ }