code: @Override
  	public <E> E get(Class<E> clazz, Object key) throws ConcurrentModificationException {
  		if (clazz == null) {
  			throw new IllegalArgumentException("'clazz' must not be [" + clazz + "]");
  		}
  		
  		if (key == null) {
  			throw new IllegalArgumentException("'id' must not be [" + key + "]");
  		}
  		
  		if (!isTransactional()) {
  			ResourceManager<Transaction> manager = new AppEngineResourceManager(datastore());
  			return manager.get(clazz, key);
  		} else {
  			return ((AppEngineGlobalTransaction) transaction.get()).coordinator().get(clazz, key);
  		}
  	}
docs: Returns the entity instance corresponding to the specified key.
  This method returns {@code null} if the entity is not found.
  
  @param <E> The entity type.
  @param clazz The entity type that you want to get.
  @param key The key corresponding to the entity that you want to get.
  @return The entity instance corresponding to the specified key.
  @throws ConcurrentModificationException If the entity corresponding to
  the specified key is being modified by the other transaction.
  @see AppEngineResourceManager#get(Class, Object)