return func.emitError() << "'width' attribute is not set or not an integer";
  }
  fbb.Int("width", width.getInt());

  auto string_separator =
      mlir::dyn_cast_or_null<StringAttr>(attrs.get("string_separator"));
  if (!string_separator) {
    return func.emitError()
           << "'string_separator' attribute is not set or not a string";
  }
  // StringAttrs are not guaranteed to be NUL terminated, but flexbuffers