Created by: zhouwei25

resolve #20977

fix Issue: https://github.com/PaddlePaddle/Paddle/issues/20977

Users says he still don't know how to use this OP after reading the example code, so increase example code 2.

Fix wrong description of API doc:

• Some numpy operations (such as +/-/shape) do not support LodTenosr and must be actively converted to numpy.