code: public PersistenceUnitMetadata<EntityMappings<T>> getOrCreatePersistenceUnitMetadata()
     {
        Node node = childNode.getOrCreate("persistence-unit-metadata");
        PersistenceUnitMetadata<EntityMappings<T>> persistenceUnitMetadata = new PersistenceUnitMetadataImpl<EntityMappings<T>>(this, "persistence-unit-metadata", childNode, node);
        return persistenceUnitMetadata;
     }
docs: If not already created, a new <code>persistence-unit-metadata</code> element with the given value will be created.
  Otherwise, the existing <code>persistence-unit-metadata</code> element will be returned.
  @return  a new or existing instance of <code>PersistenceUnitMetadata<EntityMappings<T>></code>