Fix to check body identity in helper function
Fix to check body identity in helper function

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