toContext method Null safety

Implementation

Context toContext(){
  var exception = _getException();
  final func = _dll_handle.lookupFunction<_RStoContext, _RStoContext_dart>
    (_c_namespace + 'RawSample_toContext');

  final ctxPointer = func(this._impl, exception);

  checkException(exception, _dll_handle);

  return Context(_dll_handle, ctxPointer);
}