code: protected boolean isFiltered(Param param) {
  		AbstractElement elementToParse = param.elementToParse;
  		while (elementToParse != null) {
  			if (isFiltered(elementToParse, param)) {
  				return true;
  			}
  			elementToParse = getEnclosingSingleElementGroup(elementToParse);
  		}
  		return false;
  	}
docs: Returns true if the grammar element that is associated with the given param is filtered due to guard conditions
  of parameterized rules in the current call stack.
  
  If the grammar element is the only element contained in a group, its container is checked, too.
  
  @see #isFiltered(AbstractElement, Param)