fix bug in proteins example (#263)
fix bug in proteins example (#263)

* fix bug in proteins example

* update

Co-authored-by: taoqian <6157a4a8268c30ec9bc447caf81ffe21facdd965@alibaba-inc.com>
Co-authored-by: rusty1s <a3d6bab3ad60d8bc593a709a9d29dfbf7a36a1bf@tu-dortmund.de>
snap-stanford/ogb