pub fn sub_assign(&mut self, other: SepticCurve<F>) {
        let result = self.add_incomplete(other.neg());
        self.x = result.x;
        self.y = result.y;
    }
Subtract assigns an elliptic curve point, assuming that the subtraction doesn't lead to the
exception cases of weierstrass addition.
crates/stark/src/septic_curve.rs