Refactor: avoid `_[0]`
Refactor: avoid `_[0]`

okuta/chainer,niboshi/chainer,hvy/chainer,hvy/chainer,niboshi/chainer,okuta/chainer,wkentaro/chainer,pfnet/chainer,okuta/chainer,wkentaro/chainer,chainer/chainer,wkentaro/chainer,niboshi/chainer,hvy/chainer,tkerola/chainer,okuta/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,hvy/chainer,chainer/chainer,chainer/chainer,chainer/chainer,niboshi/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,wkentaro/chainer