code: public Section mbean(String name, MBeanRule.Consumer config) {
          MBeanRule rule = new MBeanRule(name);
          config.accept(rule);
          this.rules.add(rule);
          return this;
      }
docs: Define a rule for a given MBean.
  
  @param name   The mbean name or pattern.
  @param config Configuration.
  @return This section.