Modify to use brace initialization.
Modify to use brace initialization.

Co-Authored-By: ktnyt <0e0438a48fc25a3ca370795b54ad59909abde08a@users.noreply.github.com>
niboshi/chainer,okuta/chainer,wkentaro/chainer,hvy/chainer,tkerola/chainer,pfnet/chainer,hvy/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,chainer/chainer,chainer/chainer,niboshi/chainer,niboshi/chainer,okuta/chainer,keisuke-umezawa/chainer,wkentaro/chainer,keisuke-umezawa/chainer,chainer/chainer,niboshi/chainer,wkentaro/chainer,chainer/chainer,okuta/chainer,hvy/chainer,hvy/chainer,okuta/chainer,wkentaro/chainer