src/main/java/org/organicdesign/fp/StaticImports.java
@SafeVarargs
    public static <T> MutableSet<T> mutableSet(T... items) {
        MutableSet<T> ret = PersistentHashSet.emptyMutable();
        if (items == null) { return ret; }
        for (T t : items) {
            ret.put(t);
        }
        return ret;
    }
@SafeVarargs
    public static <T> MutableSet<T> mutableSet(T... items) {
        MutableSet<T> ret = PersistentHashSet.emptyMutable();
        if (items == null) { return ret; }
        for (T t : items) {
            ret.put(t);
        }
        return ret;
    }
Returns a new MutableSet of the values.  This data definition method is one of the few
methods in this project that support varargs.  If the input contains duplicate elements, later
values overwrite earlier ones.