GitLab

* update graphdataloader in docs

* fix

* update examples

* fix sagpool
Co-authored-by: Quan (Andy) Gan <coin2028@hotmail.com>

* add sagpool example for pytorch backend

* polish sagpool example for pytorch backend

* [Example] SAGPool: use std variance

* [Example] SAGPool: change to std

* add sagpool example to index page

* add graph property prediction tag to sagpool
Co-authored-by: zhangtianqi <tianqizh@amazon.com>