def create_db_subnet_group(DBSubnetGroupName=None, DBSubnetGroupDescription
    =None, SubnetIds=None, Tags=None):
    """
    Creates a new DB subnet group. DB subnet groups must contain at least one subnet in at least two AZs in the region.
    See also: AWS API Documentation
    
    Examples
    This example creates a DB subnet group.
    Expected Output:
    
    :example: response = client.create_db_subnet_group(
        DBSubnetGroupName='string',
        DBSubnetGroupDescription='string',
        SubnetIds=[
            'string',
        ],
        Tags=[
            {
                'Key': 'string',
                'Value': 'string'
            },
        ]
    )
    
    
    :type DBSubnetGroupName: string
    :param DBSubnetGroupName: [REQUIRED]
            The name for the DB subnet group. This value is stored as a lowercase string.
            Constraints: Must contain no more than 255 alphanumeric characters, periods, underscores, spaces, or hyphens. Must not be default.
            Example: mySubnetgroup
            

    :type DBSubnetGroupDescription: string
    :param DBSubnetGroupDescription: [REQUIRED]
            The description for the DB subnet group.
            

    :type SubnetIds: list
    :param SubnetIds: [REQUIRED]
            The EC2 Subnet IDs for the DB subnet group.
            (string) --
            

    :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: {
        'DBSubnetGroup': {
            'DBSubnetGroupName': 'string',
            'DBSubnetGroupDescription': 'string',
            'VpcId': 'string',
            'SubnetGroupStatus': 'string',
            'Subnets': [
                {
                    'SubnetIdentifier': 'string',
                    'SubnetAvailabilityZone': {
                        'Name': 'string'
                    },
                    'SubnetStatus': 'string'
                },
            ],
            'DBSubnetGroupArn': 'string'
        }
    }
    
    
    :returns: 
    CreateDBSubnetGroup
    ModifyDBSubnetGroup
    DescribeDBSubnetGroups
    DeleteDBSubnetGroup
    
    """
    pass
