@Override
    public <VO, VR> KTable<K, VR> outerJoin(final KTable<K, VO> other,
                                            final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                            final Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized) {
        return outerJoin(other, joiner, NamedInternal.empty(), materialized);
    }
The implementation class of {@link KTable}.

@param <K> the key type
@param <S> the source's (parent's) value type
@param <V> the value type
streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableImpl.java