docs: protected static boolean isFileExists(IPackageFragment packageFragment, String filename, String extension) {
  		if (packageFragment != null) {
  			final IResource resource = packageFragment.getResource();
  			if (resource instanceof IFolder) {
  				final IFolder folder = (IFolder) resource;
  				if (folder.getFile(filename + "." + extension).exists()) { //$NON-NLS-1$
  					return true;
  				}
  			}
  		}
  		return false;
  	}