Fix using map function for py2/py3 compatibility.
Fix using map function for py2/py3 compatibility.

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