GitLab

* g.edata and g.ndata support multiple ntype and etype

* Add test case

* support g.srcdata and g.dstdata

* Fix test

* lint

* Fix

* Fix some comments

* lint
Co-authored-by: Ubuntu <ubuntu@ip-172-31-51-214.ec2.internal>
Co-authored-by: Mufei Li <mufeili1996@gmail.com>