added missing import
added missing import

chainer/chainer,aonotas/chainer,jnishi/chainer,wkentaro/chainer,keisuke-umezawa/chainer,hvy/chainer,jnishi/chainer,wkentaro/chainer,ktnyt/chainer,okuta/chainer,okuta/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,chainer/chainer,pfnet/chainer,jnishi/chainer,niboshi/chainer,rezoo/chainer,keisuke-umezawa/chainer,chainer/chainer,okuta/chainer,hvy/chainer,hvy/chainer,keisuke-umezawa/chainer,jnishi/chainer,keisuke-umezawa/chainer,ktnyt/chainer,ktnyt/chainer,anaruse/chainer,niboshi/chainer,tkerola/chainer,niboshi/chainer,chainer/chainer,ronekko/chainer,wkentaro/chainer,hvy/chainer,ktnyt/chainer