public KTableValueGetter<K, KeyValue<K1, V1>> get() {
                return new KTableMapValueGetter(parentValueGetterSupplier.get());
            }
KTable repartition map functions are not exposed to public APIs, but only used for keyed aggregations.
<p>
Given the input, it can output at most two records (one mapped from old value and one mapped from new value).
streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableRepartitionMap.java