GitLab

* enhance EGATConv| nfeats as tuples

* egatconv modified for bipartite graphs

* modified docstrings

* added/modified unittests for EGATConv

* Update egatconv.py

* rectified lint errors
Co-authored-by: rijulizer <riju.mukherjee@gmail.com>
Co-authored-by: Mufei Li <mufeili1996@gmail.com>