Fix import error
Fix import error

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