code: @Override
      public Set<EntityType<?>> getEntities()
      {
          Set<EntityType<?>> entities = null;
          if (entityTypes != null)
          {
              entities = new HashSet<EntityType<?>>(entityTypes.values());
          }
          return entities;
      }
docs: /*
  (non-Javadoc)
  
  @see javax.persistence.metamodel.Metamodel#getEntities()