code: public static Schedulers stopAll() {
          createSingleton();
          if (instance.runningSchedullers.isEmpty()) {
              throw new IllegalStateException("No schedulers available.");
          }
  
          for (Entry<String, ScheduledFuture<?>> entry : instance.runningSchedullers.entrySet()) {
              ScheduledFuture<?> future = entry.getValue();
              future.cancel(true);
              Schedulers.decreaseNoOfSchedullers();
              Schedulers.decreaseNoOfRunningSchedullers();
          }
  
          return instance;
      }
docs: Stop all.
  
  @return the schedulers