def METHOD_NAME(self, destination_region, grant_name, retention_period):
    if grant_name:
        self.client.METHOD_NAME(
            ClusterIdentifier=self.cluster_name,
            DestinationRegion=destination_region,
            RetentionPeriod=retention_period,
            SnapshotCopyGrantName=grant_name,
        )
    else:
        self.client.METHOD_NAME(
            ClusterIdentifier=self.cluster_name,
            DestinationRegion=destination_region,
            RetentionPeriod=retention_period,
        )