docs: @Override
      public Object saveState(final FacesContext context)
      {
          if (context == null)
          {
              throw new NullPointerException("context");
          }
  
          if (!initialStateMarked())
          {
             //Full state saving.
             return this.validationGroups;
          }
          else if (DEFAULT_VALIDATION_GROUP_NAME.equals(this.validationGroups))
          {
              // default validation groups can be saved as null.
              return null;
          }
          else
          {
              // Save it fully. Remember that by MYFACES-2528
              // validationGroups needs to be stored into the state
              // because this value is often susceptible to use in "combo"
              return this.validationGroups;
          }
      }