docs: public static UserExecutorConfiguration of(ExecutorType type, int num) {
          ArgumentUtils.check("type", type).notNull();
          UserExecutorConfiguration configuration = of(type);
          configuration.type = type;
          switch (type) {
              case FIXED:
                  configuration.nThreads = num;
                  break;
              case SCHEDULED:
                  configuration.corePoolSize = num;
                  break;
              case WORK_STEALING:
                  configuration.parallelism = num;
                  break;
              default:
          }
          return configuration;
      }