| B.Text (attrs, t) -> B.Text (((Some "helm", "xref", id) :: attrs), t)
| _ -> assert false (* TODO, add_xref is meaningful for all boxes *)
| B.Text (attrs, t) -> B.Text (((Some "helm", "xref", id) :: attrs), t)
| _ -> assert false (* TODO, add_xref is meaningful for all boxes *)