def METHOD_NAME(client):
    resp = client.create_db_instance(
        DBInstanceIdentifier=DB_INSTANCE_IDENTIFIER,
        AllocatedStorage=10,
        Engine="postgres",
        DBName="staging-postgres",
        DBInstanceClass="db.m1.small",
        MasterUsername="root",
        MasterUserPassword="hunter2",
        Port=1234,
        DBSecurityGroups=["my_sg"],
    )
    return resp["DBInstance"]["DBInstanceIdentifier"]