public Consumed<K, V> withKeySerde(final Serde<K> keySerde) {
        return new Consumed<K, V>(keySerde, valueSerde, timestampExtractor, resetPolicy, processorName);
    }
Configure the instance of {@link Consumed} with a key {@link Serde}.

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

@return a new instance of {@link Consumed}
streams/src/main/java/org/apache/kafka/streams/kstream/Consumed.java