Function render_completion_operator 

pub fn render_completion_operator<'scope, T, F>(
    scope: Scope<'scope, T>,
    results_stream: StreamVec<'scope, T, Result<ProtoBatch, StorageErrorX>>,
    worker_callback: F,
)
where
    T: Timestamp,
    F: FnOnce(Result<Option<ProtoBatch>, String>) + 'static,

Render an operator that given a stream of ProtoBatches will call our worker_callback to report the results upstream.