public Map<TopicPartition, Set<String>> racksForPartition() {
        return Collections.unmodifiableMap(racksForPartition);
    }
Verifies that within the {@param racksForProcessConsumer}, a single process is only running on a single
rack. This function mutates the parameter {@param racksForProcess} to contain the resulting process
to rack mapping.

@return true if the validation was successful, and false otherwise.
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/RackAwareTaskAssignor.java