docs: @SuppressWarnings("unchecked")
      public T workerPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit) {
          assertNumericArgument(corePoolSize, true);
          assertNumericArgument(maximumPoolSize, false);
          assertSmallerEquals(corePoolSize, maximumPoolSize);
          assertNumericArgument(keepAliveTime, true);
          assertNumericArgument(keepAliveTime, true);
          this.corePoolSize = corePoolSize;
          this.maximumPoolSize = maximumPoolSize;
          this.keepAliveTime = unit.toMillis(keepAliveTime);
          return (T) this;
      }