public Set<String> findGroups(String regionName) {
    Set<String> results = new HashSet<>();
    Set<String> groups = persistenceService.getGroups();
    for (String group : groups) {
      CacheConfig existing = persistenceService.getCacheConfig(group, false);
      if (existing != null && existing.findRegionConfiguration(regionName) != null) {
        results.add(group);
      }
    }
    return results;
  }
this returns a map of CacheElement with this id, with the group as the key of the map
geode-core/src/main/java/org/apache/geode/management/internal/configuration/validators/MemberValidator.java