@Override
        public String toString() {
            return "Sub-topology: " + id + " for global store (will not generate tasks)\n"
                    + "    " + source.toString() + "\n"
                    + "    " + processor.toString() + "\n";
        }
@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