@SuppressWarnings("unchecked")
    @Override
    public Optional<T12> get12() {
        return Optional.ofNullable((T12) values[12]);
    }
Constructs a {@link MutableTuple} of type {@link MutableTuple21}.
common-parent/tuple/src/main/java/com/speedment/common/tuple/internal/mutable/MutableTuple21Impl.java