code: public String getFramePath (String action, String type, Set<String> existentPaths)
      {
          return _frameProvider.getFramePath(this, action, type, existentPaths);
      }
docs: Returns the path to the image frames for the specified action animation or null if no
  animation for the specified action is available for this component.
  
  @param type null for the normal action frames or one of the custom action sub-types:
  {@link StandardActions#SHADOW_TYPE}, etc.
  
  @param existentPaths the set of all paths for which there are valid frames.