add test for add_hook return self
add test for add_hook return self

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