Use copy-ctor to deep-copy
Use copy-ctor to deep-copy

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