@Override
        public String toString() {
            return "Processor: " + name + " (stores: " + stores + ")\n      --> "
                + nodeNames(successors) + "\n      <-- " + nodeNames(predecessors);
        }
@return names of all source topics, including the application id/named topology prefix for repartition sources
streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalTopologyBuilder.java