fn assert_digest_zero_v2(&mut self, is_real: Felt<C::F>, digest: SepticDigest<Felt<C::F>>) {
        let zero = SepticDigest::<SymbolicFelt<C::F>>::zero();
        for (digest_limb_x, zero_limb_x) in digest.0.x.0.into_iter().zip_eq(zero.0.x.0.into_iter())
        {
            self.assert_felt_eq(is_real * digest_limb_x, is_real * zero_limb_x);
        }
        for (digest_limb_y, zero_limb_y) in digest.0.y.0.into_iter().zip_eq(zero.0.y.0.into_iter())
        {
            self.assert_felt_eq(is_real * digest_limb_y, is_real * zero_limb_y);
        }
    }
Asserts that the `digest` is the zero digest when `is_real` is non-zero.
crates/recursion/compiler/src/circuit/builder.rs