docs: private String genChoiceEntry(StructureDefinition sd, ElementDefinition ed, String id, String base, ElementDefinition.TypeRefComponent typ) {
      ST shex_choice_entry = tmplt(ELEMENT_TEMPLATE);
  
      String ext = typ.getCode();
      shex_choice_entry.add("id", "fhir:" + base+Character.toUpperCase(ext.charAt(0)) + ext.substring(1) + " ");
      shex_choice_entry.add("card", "");
      shex_choice_entry.add("defn", genTypeRef(sd, ed, id, typ));
      shex_choice_entry.add("comment", " ");
      return shex_choice_entry.render();
    }