'Modify a parameter group for your account.
:type name: string
:param name: The name of the new parameter group
:type parameters: list of :class:`boto.rds.parametergroup.Parameter`
:param parameters: The new parameters
:rtype: :class:`boto.rds.parametergroup.ParameterGroup`
:return: The newly created ParameterGroup'

def modify_db_subnet_group(self, name, description=None, subnet_ids=None):

    params = {'DBSubnetGroupName': name}
    if (description is not None):
        params['DBSubnetGroupDescription'] = description
    if (subnet_ids is not None):
        self.build_list_params(params, subnet_ids, 'SubnetIds.member')
    return self.get_object('ModifyDBSubnetGroup', params, DBSubnetGroup)
