code: public static boolean isPackagePrivate(Element element) {
  		if (isPublic(element)) {
  			return false;
  		} else if (isProtected(element)) {
  			return false;
  		} else if (isPrivate(element)) {
  			return false;
  		}
  		return true;
  	}
docs: Tests if the given element has the package-private visibility.
  @param element
  @return true if package-private, false otherwise
  @author vvakame