Added possible shapes of b to solve docs
Added possible shapes of b to solve docs

niboshi/chainer,hvy/chainer,hvy/chainer,niboshi/chainer,chainer/chainer,okuta/chainer,chainer/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,hvy/chainer,chainer/chainer,pfnet/chainer,wkentaro/chainer,okuta/chainer,niboshi/chainer,wkentaro/chainer,chainer/chainer,hvy/chainer,wkentaro/chainer,okuta/chainer