Fix calling super class method.
Fix calling super class method.

okuta/chainer,jnishi/chainer,niboshi/chainer,chainer/chainer,chainer/chainer,ysekky/chainer,ktnyt/chainer,cupy/cupy,keisuke-umezawa/chainer,chainer/chainer,wkentaro/chainer,jnishi/chainer,chainer/chainer,tkerola/chainer,delta2323/chainer,cupy/cupy,cupy/cupy,jnishi/chainer,jnishi/chainer,hvy/chainer,ktnyt/chainer,aonotas/chainer,rezoo/chainer,ktnyt/chainer,ronekko/chainer,kiyukuta/chainer,okuta/chainer,kashif/chainer,keisuke-umezawa/chainer,pfnet/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,anaruse/chainer,wkentaro/chainer,niboshi/chainer,ktnyt/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,hvy/chainer,wkentaro/chainer,hvy/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,cupy/cupy