code: public <E> E load(Class<E> entityClass, DatastoreKey parentKey, long id) {
      EntityMetadata entityMetadata = EntityIntrospector.introspect(entityClass);
      Key nativeKey;
      if (parentKey == null) {
        nativeKey = entityManager.newNativeKeyFactory().setKind(entityMetadata.getKind()).newKey(id);
      } else {
        nativeKey = Key.newBuilder(parentKey.nativeKey(), entityMetadata.getKind(), id).build();
      }
      return fetch(entityClass, nativeKey);
    }
docs: Loads and returns the entity with the given ID. The entity kind is determined from the supplied
  class.
  
  @param entityClass
  the entity class
  @param parentKey
  the parent key of the entity.
  @param id
  the ID of the entity
  @return the Entity object or <code>null</code>, if the the entity with the given ID does not
  exist in the Cloud Datastore.
  @throws EntityManagerException
  if any error occurs while inserting.