code: public CmsResourceFilter addRequireState(CmsResourceState state) {
  
          CmsResourceFilter extendedFilter = (CmsResourceFilter)clone();
  
          extendedFilter.m_state = state;
          extendedFilter.m_filterState = REQUIRED;
          extendedFilter.updateCacheId();
  
          return extendedFilter;
      }
docs: Returns an extended filter to guarantee a distinct resource state of the filtered resources.<p>
  
  @param state the required resource state
  @return a filter requiring the given resource state