docs: public void removeRuleFlow(String id) {
          ProcessPackage rtp = (ProcessPackage) getResourceTypePackages().get(ResourceType.BPMN2);
          if (rtp == null || rtp.lookup(id) == null) {
              throw new IllegalArgumentException("The rule flow with id [" + id + "] is not part of this package.");
          }
          rtp.remove(id);
      }