Fix docstring.
Fix docstring.

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