def METHOD_NAME(self, n: int) -> None:
    """
    Increase the the number of idle workers by C{n}.
    @param n: The number of new idle workers to create.
    @type n: L{int}
    """
    self._quit.check()
    @self._coordinator.do
    def createOneWorker() -> None:
        for x in range(n):
            worker = self._createWorker()
            if worker is None:
                return
            self._recycleWorker(worker)