@SuppressWarnings("deprecation") // Old PAPI. Needs to be migrated.
    private <K, V> org.apache.kafka.streams.processor.ProcessorSupplier<K, V> defineWithStoresOldAPI(final Supplier<org.apache.kafka.streams.processor.Processor<K, V>> supplier,
                                                                                                     final Set<StoreBuilder<?>> stores) {
        return new org.apache.kafka.streams.processor.ProcessorSupplier<K, V>() {
            @Override
            public org.apache.kafka.streams.processor.Processor<K, V> get() {
                return supplier.get();
            }

            @Override
            public Set<StoreBuilder<?>> stores() {
                return stores;
            }
        };
    }
A processor that stores each key-value pair in an in-memory key-value store registered with the context.
streams/src/test/java/org/apache/kafka/streams/processor/internals/ProcessorTopologyTest.java