Fix docstring slightly.
Fix docstring slightly.

cupy/cupy,kiyukuta/chainer,cupy/cupy,keisuke-umezawa/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,pfnet/chainer,niboshi/chainer,wkentaro/chainer,ysekky/chainer,okuta/chainer,kashif/chainer,ktnyt/chainer,jnishi/chainer,hvy/chainer,wkentaro/chainer,chainer/chainer,delta2323/chainer,okuta/chainer,chainer/chainer,ktnyt/chainer,aonotas/chainer,okuta/chainer,chainer/chainer,cupy/cupy,hvy/chainer,anaruse/chainer,niboshi/chainer,jnishi/chainer,hvy/chainer,ktnyt/chainer,jnishi/chainer,keisuke-umezawa/chainer,chainer/chainer,jnishi/chainer,tkerola/chainer,rezoo/chainer,wkentaro/chainer,niboshi/chainer,hvy/chainer,ktnyt/chainer,ronekko/chainer,cupy/cupy,okuta/chainer,niboshi/chainer,wkentaro/chainer