GitLab

* [Example]Variational Graph Auto-Encoders

* change dgl dataset to single directional graph

* clean code

* refresh

* fix bug

* fix bug

* fix bug

* add gpu
Co-authored-by: Tianjun Xiao <xiaotj1990327@gmail.com>
Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>