let string_of_tr_id (id : Doc_types.tr_id) : string =
match id.fld_id_tag, id.fld_id_name, id.fld_id_scope with
|Cs_tag tag, Cs_name name, Some scope -> String.concat ":" [tag; name; string_of_tu_scope scope]
|Cs_tag tag, Cs_name name, None -> String.concat ":" [tag; name]