Update docstring for scheduler.set_result_callback
Updates the docstring to provide more information about when a None
result should be expected.
@@ -146,7 +146,8 @@ pub trait Scheduler {
/// Sets a callback to receive results from processing batches. The order
/// the results are received is not guarenteed to be the same order as the
/// batches were added with `add_batch`. If callback is called with None,
- /// all batch results have been sent.
+ /// all batch results have been sent (only used when the scheduler has been
+ /// finalized and no more batches will be added).
fn set_result_callback(
&mut self,
callback: Box<Fn(Option<BatchExecutionResult>) + Send>,
