immediately terminate the source
Do not pull the item from the source and halt processing until the provided signal is invoked
Pull the item just processed from the source and immediately process the next item when it becomes available
Pull the item just processed from the source and do not process any further items
Do not pull the item from the source and stop processing
A PullAction is the return type of a processing function passed to Source.
pullWhile
method. It signals to the source what action should be taken after the processing function has processed the next item from the source.