validation set stadia was we're taking a gradient through a gradient so the parameters theta T plus 1 that are responsible for this validation loss reward signal we're trying to update the teacher network with our updated by taking the parameters theta T and then updating them with a gradient so we want to know how much each parameter infi is responsible for the gradient that updates this so you're taking the derivative with respect to the-- of this validation loss well fee is you know contributes to this validation