code: protected void registerPostProcessorAction(String actionId) {
          if( postProcessorActionIds.contains( actionId ) ) {
              throw new IllegalArgumentException( "Post-processor Action '" + actionId + "' is already registered" );
          }
          postProcessorActionIds.add( actionId );
      }
docs: Register a post-processor action. The action id specified must not conflict with
  any other action registered. Subclasses that provide additional post-processor
  actions MUST call this method to register them.
  @param actionId Id of post-processor action to register