code: Map<String, Object> getUnderlyingMap()
      {
          StateHelper stateHelper = _component.getStateHelper(false);
          Map<String, Object> attributes = null;
          if (stateHelper != null)
          {
              attributes = (Map<String, Object>) stateHelper.get(UIComponentBase.PropertyKeys.attributesMap);
          }
          return attributes == null ? Collections.EMPTY_MAP : attributes;
      }
docs: Return the map containing the attributes.
  <p/>
  This method is package-scope so that the UIComponentBase class can access it
  directly when serializing the component.