Invoked for each element to produce a (possibly empty) sequence of output elements.
Invoked after normal completion or error.
Invoked after handing off the elements produced from one input element to the downstream consumers to determine whether to end stream processing at this point; in that case the upstream subscription is canceled.
Name of this transformation step.
Invoked when failure is signaled from upstream.
Invoked before the Transformer terminates (either normal completion or after an onError) to produce a (possibly empty) sequence of elements in response to the end-of-stream event.
Contains a non-empty option with the error causing the termination or an empty option if the Transformer was completed normally