'Creates a new DB subnet group. DB subnet groups must contain
at least one subnet in at least two AZs in the region.
:type db_subnet_group_name: string
:param db_subnet_group_name: The name for the DB subnet group. This
value is stored as a lowercase string.
Constraints: Must contain no more than 255 alphanumeric characters or
hyphens. Must not be "Default".
Example: `mySubnetgroup`
:type db_subnet_group_description: string
:param db_subnet_group_description: The description for the DB subnet
group.
:type subnet_ids: list
:param subnet_ids: The EC2 Subnet IDs for the DB subnet group.
:type tags: list
:param tags: A list of tags. Tags must be passed as tuples in the form
[(\'key1\', \'valueForKey1\'), (\'key2\', \'valueForKey2\')]'

def create_db_subnet_group(self, db_subnet_group_name, db_subnet_group_description, subnet_ids, tags=None):

    params = {'DBSubnetGroupName': db_subnet_group_name, 'DBSubnetGroupDescription': db_subnet_group_description}
    self.build_list_params(params, subnet_ids, 'SubnetIds.member')
    if (tags is not None):
        self.build_complex_list_params(params, tags, 'Tags.member', ('Key', 'Value'))
    return self._make_request(action='CreateDBSubnetGroup', verb='POST', path='/', params=params)
