Fix docstring: Function -> FunctionNode
Fix docstring: Function -> FunctionNode

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