Identify the simile in the following passage: hueitse said to chuangtse, "i have a large tree, called the ailanthus. its trunk is so irregular and knotty that it cannot be measured out for planks; while its branches are so twisted that they cannot be cut out into discs or squares. it stands by the roadside, but no carpenter will look at it. your words are like that tree - big and useless, of no concern to the world."