private RegionAttributesCreation peekRegionAttributesContext(String dependentElement) {
    Object a = stack.peek();
    if (!(a instanceof RegionAttributesCreation)) {
      throw new CacheXmlException(
          String.format("A %s must be defined in the context of region-attributes.",
              dependentElement));
    }
    return (RegionAttributesCreation) a;
  }
When a <code>region-idle-time</code> element is finished, the {@link ExpirationAttributes} are
on top of the stack followed by the {@link RegionAttributesCreation} to which the expiration
attributes are assigned.
geode-core/src/main/java/org/apache/geode/internal/cache/xmlcache/CacheXmlParser.java