code: @Override
  	public void put(Object entity) throws EntityExistsException {
  		if (entity == null) {
  			throw new IllegalArgumentException("'entity' must not be [" + entity + "]");
  		}
  		
  		assertTransactional();
  		((AppEngineGlobalTransaction) transaction.get()).coordinator().put(entity);
  	}
docs: Puts the specified entity instance into App Engine Datastore newly.
  This method must be invoked under a transaction. This method throws
  {@code EntityExistsException} if the entity that has the same key as
  the specified entity has been already stored.
  
  @param entity The entity instance to be put into App Engine Datastore.
  @throws EntityExistsException If the entity that has the same key as the
  specified entity has already existed.