void initializeRegions(Map<String, Region<?, ?>> declarativeRegions, Cache cache) {
    for (Region region : declarativeRegions.values()) {
      RegionCreation regionCreation = (RegionCreation) region;
      regionCreation.createRoot(cache);
    }
  }
Fills in the contents of a {@link Cache} based on this creation object's state.
geode-core/src/main/java/org/apache/geode/internal/cache/xmlcache/CacheCreation.java