modify flake8 error
modify flake8 error

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