save method Null safety
Implementation
void save(String filePath, bool allowOverwrite) {
  var exception = _getException();
  final saveConstructor = _dll_handle.lookupFunction<_DynamicTemplateIndex_save_c, _DynamicTemplateIndex_save_dart>(_c_namespace + "DynamicTemplateIndex_save");
  saveConstructor(_impl, filePath.toNativeUtf8(), allowOverwrite, exception);
  checkException(exception, _dll_handle);
}