same code for all backends
same code for all backends

hvy/chainer,hvy/chainer,hvy/chainer,wkentaro/chainer,niboshi/chainer,niboshi/chainer,chainer/chainer,chainer/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,wkentaro/chainer,wkentaro/chainer,okuta/chainer,chainer/chainer,chainer/chainer,niboshi/chainer,pfnet/chainer,okuta/chainer,wkentaro/chainer,okuta/chainer