public static <K, V> Grouped<K, V> keySerde(final Serde<K> keySerde) {
        return new Grouped<>(null, keySerde, null);
    }
Create a {@link Grouped} instance with the provided keySerde. If {@code null} the default key serde from config will be used.

@param keySerde
       the Serde used for serializing the key. If {@code null} the default key serde from config will be used

@param <K> the key type
@param <V> the value type

@return a new {@link Grouped} configured with the keySerde

@see KStream#groupByKey(Grouped)
@see KStream#groupBy(KeyValueMapper, Grouped)
@see KTable#groupBy(KeyValueMapper, Grouped)
streams/src/main/java/org/apache/kafka/streams/kstream/Grouped.java