@VisibleForTesting
  public Set getRealClientIds() {
    return clientMap == null ? Collections.emptySet()
        : Collections.unmodifiableSet(clientMap.realIDs.keySet());
  }
Return the set of real client proxy ids

@return the set of real client proxy ids
geode-core/src/main/java/org/apache/geode/internal/cache/FilterProfile.java