{"ast_node_type":"function","tokens":[{"end":91,"kind":"keyword","start":0,"text":"fn"}]}
    fn insert(&mut self, tcx: TyCtxt<'_>, fi: hir::ForeignItemId) -> Option<hir::OwnerId> {
    /// for the item, return its HirId without updating the set.
        let did = fi.owner_id.to_def_id();