Function branch_bounds 

pub fn branch_bounds(
    inp: &CertificateInput<'_>,
    held: &[HeldSide],
) -> BranchBounds

The branch NLP’s bounds for held (one per pair): the held side pinned at zero, and, on a mixed pair held at a bound, the free row given the sign the pair requires there. For pounce_nlp::mpcc::MpccTnlp::set_branch.