def update_rds_db_instance(RdsDbInstanceArn=None, DbUser=None, DbPassword=None
    ):
    """
    Updates an Amazon RDS instance.
    See also: AWS API Documentation
    
    
    :example: response = client.update_rds_db_instance(
        RdsDbInstanceArn='string',
        DbUser='string',
        DbPassword='string'
    )
    
    
    :type RdsDbInstanceArn: string
    :param RdsDbInstanceArn: [REQUIRED]
            The Amazon RDS instance's ARN.
            

    :type DbUser: string
    :param DbUser: The master user name.

    :type DbPassword: string
    :param DbPassword: The database password.

    """
    pass
