pub fn to_univariate(&self) -> Polynomial<FieldElement<F>> {
        let poly0 = self.fix_last_variable(&FieldElement::zero());
        let poly1 = self.fix_last_variable(&FieldElement::one());
        let sum0: FieldElement<F> = poly0.to_evaluations().into_iter().sum();
        let sum1: FieldElement<F> = poly1.to_evaluations().into_iter().sum();
        let diff = sum1 - &sum0;
        Polynomial::new(&[sum0, diff])
    }
Collapses the last variable by fixing it to 0 and 1,
sums the evaluations, and returns a univariate polynomial (as a Polynomial)
of the form: sum0 + (sum1 - sum0) * x.
crates/math/src/polynomial/dense_multilinear_poly.rs