src/main/java/org/organicdesign/fp/StaticImports.java
@SafeVarargs
    static public <T> ImRrbt<T> rrb(T... items) {
        if ( (items == null) || (items.length < 1) ) { return RrbTree.empty(); }
        return mutableRrb(items).immutable();
    }
@SafeVarargs
    static public <T> ImRrbt<T> rrb(T... items) {
        if ( (items == null) || (items.length < 1) ) { return RrbTree.empty(); }
        return mutableRrb(items).immutable();
    }
Returns a new immutable RRB Tree {@link ImRrbt} of the given items.  An RRB Tree
is an immutable list that supports random inserts, split, and join (the PersistentVector does
not).  If you build it entirely with random
inserts, then the RRB tree get() method may be about 5x slower.  Otherwise, performance
is about the same.

This data definition method is one of the few methods in this project that support varargs.