class Async::Waiter

@parameter finished [Async::Condition] The condition to signal when a task completes.
@parameter parent [Interface(:async) | Nil] The parent task to use for asynchronous operations.

Create a waiter instance.

def initialize(parent: nil, finished: Async::Condition.new)
	@finished = finished
	@done = []
	
	@parent = parent
end