src/main/java/org/organicdesign/fp/StaticImports.java
public static <T extends Comparable<T>> ImSortedSet<T> sortedSet(Iterable<T> items) {
        return PersistentTreeSet.of(items);
    }
public static <T extends Comparable<T>> ImSortedSet<T> sortedSet(Iterable<T> items) {
        return PersistentTreeSet.of(items);
    }
Returns a new PersistentTreeSet of the given comparable items.