def purchase_reserved_db_instances_offering(ReservedDBInstancesOfferingId=
    None, ReservedDBInstanceId=None, DBInstanceCount=None, Tags=None):
    """
    Purchases a reserved DB instance offering.
    See also: AWS API Documentation
    
    Examples
    This example purchases a reserved DB instance offering that matches the specified settings.
    Expected Output:
    
    :example: response = client.purchase_reserved_db_instances_offering(
        ReservedDBInstancesOfferingId='string',
        ReservedDBInstanceId='string',
        DBInstanceCount=123,
        Tags=[
            {
                'Key': 'string',
                'Value': 'string'
            },
        ]
    )
    
    
    :type ReservedDBInstancesOfferingId: string
    :param ReservedDBInstancesOfferingId: [REQUIRED]
            The ID of the Reserved DB instance offering to purchase.
            Example: 438012d3-4052-4cc7-b2e3-8d3372e0e706
            

    :type ReservedDBInstanceId: string
    :param ReservedDBInstanceId: Customer-specified identifier to track this reservation.
            Example: myreservationID
            

    :type DBInstanceCount: integer
    :param DBInstanceCount: The number of instances to reserve.
            Default: 1
            

    :type Tags: list
    :param Tags: A list of tags.
            (dict) --Metadata assigned to an Amazon RDS resource consisting of a key-value pair.
            Key (string) --A key is the required name of the tag. The string value can be from 1 to 128 Unicode characters in length and cannot be prefixed with 'aws:' or 'rds:'. The string can only contain only the set of Unicode letters, digits, white-space, '_', '.', '/', '=', '+', '-' (Java regex: '^([\\p{L}\\p{Z}\\p{N}_.:/=+\\-]*)$').
            Value (string) --A value is the optional value of the tag. The string value can be from 1 to 256 Unicode characters in length and cannot be prefixed with 'aws:' or 'rds:'. The string can only contain only the set of Unicode letters, digits, white-space, '_', '.', '/', '=', '+', '-' (Java regex: '^([\\p{L}\\p{Z}\\p{N}_.:/=+\\-]*)$').
            
            

    :rtype: dict
    :return: {
        'ReservedDBInstance': {
            'ReservedDBInstanceId': 'string',
            'ReservedDBInstancesOfferingId': 'string',
            'DBInstanceClass': 'string',
            'StartTime': datetime(2015, 1, 1),
            'Duration': 123,
            'FixedPrice': 123.0,
            'UsagePrice': 123.0,
            'CurrencyCode': 'string',
            'DBInstanceCount': 123,
            'ProductDescription': 'string',
            'OfferingType': 'string',
            'MultiAZ': True|False,
            'State': 'string',
            'RecurringCharges': [
                {
                    'RecurringChargeAmount': 123.0,
                    'RecurringChargeFrequency': 'string'
                },
            ],
            'ReservedDBInstanceArn': 'string'
        }
    }
    
    
    """
    pass
