'Schedule a list of :class:`_Signal` for delivery.'

def _schedule(self, signals):

    self._input_queue.extend(signals)
    for link in {sig.link for sig in signals}:
        contents = self.link_contents(link)
        if any(((value is not None) for value in contents.values())):
            state = SchemeLink.Active
        else:
            state = SchemeLink.Empty
        link.set_runtime_state((state | SchemeLink.Pending))
    if signals:
        self.updatesPending.emit()
    self._update()
