@Override public X2<V0, V1> get(Object o) { return containsKey(o)? Tuple.X2(m0.get(o), m1.get(o)): null; }
@Override public V get(Object o) { if (!(o instanceof U2)) { return null; } @SuppressWarnings("unchecked") U2<K0, K1> u = (U2<K0, K1>)o; return (u.type == 0)? m0.get(u.getT0()): m1.get(u.getT1()); }