fn assert_is_base_element<I: Into<Self::Expr> + Clone>(
        &mut self,
        element: BinomialExtension<I>,
    ) {
        let base_slice = element.as_base_slice();
        let degree = base_slice.len();
        base_slice[1..degree].iter().for_each(|coeff| {
            self.assert_zero(coeff.clone().into());
        });
    }
Checks if an extension element is a base element.
crates/stark/src/air/builder.rs