Flatten a Signal[Traversable[Event[B]\]\] into a Event[B].
Flatten a Signal[Traversable[Event[B]\]\] into a Event[B]. The new Event fires the value of any inner firing Event. If multiple inner Events fire, the first one in iteration order is selected.
Flatten a Signal[Traversable[Event[B]\]\] into a Event[Traversable[Option[B]\]\] where the new Event fires whenever any of the inner events fire
Flatten a Signal[Traversable[Signal[B]\]\] into a Signal[Traversable[B]\] where the new Signal updates whenever any of the inner or the outer signal updates