public When_modifying_settings()
            {
                _configurationSettings = ConfigurationSettings.Create(
                    ("1_unchanging", "initial"),
                    ("2_modified", "initial"),
                    ("3_modified_to_same_value", "initial"),
                    ("4_deleted", "initial")

                    );

                _modifiedConfigurationSettings = _configurationSettings
                                                 .WithDeletedKeys(
                    "4_deleted")
                                                 .WithModifiedSettings(
                    ("2_modified", "modified"),
                    ("3_modified_to_same_value", "initial"),
                    ("5_new", "new"));
            }
        private async Task <IConfigurationSettings> SaveSettings(ModifiedConfigurationSettings settings)
        {
            await _streamStoreConfigRepository.WriteChanges(settings, CancellationToken.None);

            return(await _streamStoreConfigRepository.GetLatest(CancellationToken.None));
        }