GitLab

* attach positive.

* add neg_deg_sample.

* add comment.

* add neg_deg_sample for eval.

* change the edge sampler.

* rename edge sampler in KG.

* allow specifying chunk size and negative sample size separately.

* fix bugs in KG.

* add check in sampler.

* add more checks.

* fix

* add comment.

* add comments.