code: private Set<String> getResourcePaths(List<JoinableResourceBundle> bundles) {
  
  		Set<String> resourcePaths = new HashSet<>();
  
  		for (JoinableResourceBundle bundle : bundles) {
  			for (BundlePath bundlePath : bundle.getItemPathList()) {
  				resourcePaths.add(bundlePath.getPath());
  			}
  		}
  
  		return resourcePaths;
  	}
docs: Returns the list of all CSS files defined in the bundles.
  
  @param bundles
  the list of bundle
  @return the list of all CSS files defined in the bundles.