code: public final <T4, T5, T6> Tuple6<T1, T2, T3, T4, T5, T6> concat(Tuple3<T4, T5, T6> tuple) {
          return new Tuple6<>(v1, v2, v3, tuple.v1, tuple.v2, tuple.v3);
      }
docs: Concatenate a tuple to this tuple.