def __init__(self, num_features: int) -> None:
        """max(y, tau) = max(y - tau, 0) + tau = ReLU(y - tau) + tau."""
        super().__init__()
        self.num_features = num_features
        self.tau = Parameter(-torch.ones(1, num_features, 1, 1), requires_grad=True)
        self.reset_parameters()
max(y, tau) = max(y - tau, 0) + tau = ReLU(y - tau) + tau.
kornia/feature/hynet.py