

30072020 MR add nesterovs momentum to TD batch
https://stats.stackexchange.com/questions/179915/whats-the-difference-between-momentum-based-gradient-descent-and-nesterovs-acc
p_{new} = p + self.momentum^2 * m - (1 + self.momentum) * lr * g
where m is the previous weight update, and g is the current gradient with respect to the parameters p, lr is the learning rate, and self.momentum is a constant.
