Copies gradients from param_with_grad to params

        :param params: dst parameters
        :param params_with_grad: src parameters

def set_grads(params, params_with_grad):
        """
        Copies gradients from param_with_grad to params

        :param params: dst parameters
        :param params_with_grad: src parameters
        """
        for param, param_w_grad in zip(params, params_with_grad):
            if param.grad is None:
                param.grad = torch.nn.Parameter(torch.empty_like(param))
            param.grad.data.copy_(param_w_grad.grad.data)