### Question:
SelectById extends IndirectQuery implements Select<T> { public SelectById<T> prefetch(PrefetchTreeNode prefetch) { if (prefetch == null) { return this; } if (prefetches == null) { prefetches = new PrefetchTreeNode(); } prefetches.merge(prefetch); return this; } protected  SelectById(QueryRoot root, IdSpec idSpec, boolean fetchingDataRows); protected  SelectById(QueryRoot root, IdSpec idSpec); static SelectById<T> query(Class<T> entityType, Object id); static SelectById<T> query(Class<T> entityType, Map<String, ?> id); static SelectById<T> query(Class<T> entityType, ObjectId id); static SelectById<T> query(Class<T> entityType, Object firstId, Object... otherIds); static SelectById<T> query(Class<T> entityType, Collection<Object> ids); @SafeVarargs static SelectById<T> query(Class<T> entityType, Map<String, ?> firstId, Map<String, ?>... otherIds); static SelectById<T> query(Class<T> entityType, ObjectId firstId, ObjectId... otherIds); static SelectById<DataRow> dataRowQuery(Class<?> entityType, Object id); static SelectById<DataRow> dataRowQuery(Class<?> entityType, Map<String, ?> id); static SelectById<DataRow> dataRowQuery(ObjectId id); static SelectById<DataRow> dataRowQuery(Class<?> entityType, Object firstId, Object... otherIds); @SafeVarargs static SelectById<DataRow> dataRowQuery(Class<?> entityType, Map<String, ?> firstId, Map<String, ?>... otherIds); static SelectById<DataRow> dataRowQuery(ObjectId firstId, ObjectId... otherIds); @Override List<T> select(ObjectContext context); @Override T selectOne(ObjectContext context); @Override T selectFirst(ObjectContext context); @Override void iterate(ObjectContext context, ResultIteratorCallback<T> callback); @Override ResultIterator<T> iterator(ObjectContext context); @Override ResultBatchIterator<T> batchIterator(ObjectContext context, int size); SelectById<T> localCache(String cacheGroup); SelectById<T> localCache(); SelectById<T> sharedCache(String cacheGroup); SelectById<T> sharedCache(); QueryCacheStrategy getCacheStrategy(); SelectById<T> cacheStrategy(QueryCacheStrategy strategy); SelectById<T> cacheStrategy(QueryCacheStrategy strategy, String cacheGroup); String getCacheGroup(); SelectById<T> cacheGroup(String cacheGroup); boolean isFetchingDataRows(); SelectById<T> prefetch(PrefetchTreeNode prefetch); SelectById<T> prefetch(String path, int semantics); PrefetchTreeNode getPrefetches();  }### Answer:
@Test public void testPrefetch() { PrefetchTreeNode root = PrefetchTreeNode.withPath("a.b", PrefetchTreeNode.JOINT_PREFETCH_SEMANTICS); SelectById<Artist> q = SelectById.query(Artist.class, 6); q.prefetch(root); PrefetchTreeNode prefetch = q.getPrefetches(); assertNotNull(prefetch); assertNotNull(prefetch.getNode("a.b")); }