docs: public static Concurrency with(final Executor executor) {
  		if (executor instanceof ForkJoinPool) {
  			return new ForkJoinPoolConcurrency((ForkJoinPool)executor);
  		} else if (executor instanceof ExecutorService) {
  			return new ExecutorServiceConcurrency((ExecutorService)executor);
  		} else if (executor == SERIAL_EXECUTOR) {
  			return SERIAL_EXECUTOR;
  		} else {
  			return new ExecutorConcurrency(executor);
  		}
  	}