code: public PersistenceUnitMetadata<OrmDescriptor> getOrCreatePersistenceUnitMetadata()
     {
        Node node = model.getOrCreate("persistence-unit-metadata");
        PersistenceUnitMetadata<OrmDescriptor> persistenceUnitMetadata = new PersistenceUnitMetadataImpl<OrmDescriptor>(this, "persistence-unit-metadata", model, 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<OrmDescriptor></code>