Update chainer/functions/__init__.py
Update chainer/functions/__init__.py

Co-Authored-By: fiarabbit <c5c480bec7a42a802418cc3a6a6c3c50717faa1c@gmail.com>
niboshi/chainer,okuta/chainer,hvy/chainer,chainer/chainer,wkentaro/chainer,keisuke-umezawa/chainer,okuta/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,niboshi/chainer,tkerola/chainer,okuta/chainer,hvy/chainer,okuta/chainer,wkentaro/chainer,keisuke-umezawa/chainer,wkentaro/chainer,chainer/chainer,wkentaro/chainer,pfnet/chainer,hvy/chainer,chainer/chainer,hvy/chainer,niboshi/chainer,niboshi/chainer,chainer/chainer