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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_dhcp_options(self, vpc_id, cidr_block, availability_zone=None):
 """ Create a new DhcpOption :type vpc_id: str :param vpc_id: The ID of the VPC where you want to create the subnet. :type cidr_block: str :param cidr_block: The CIDR block you want the subnet to cover. :type availability_zone: str :param availability_zone: The AZ you want the subnet in :rtype: The newly created DhcpOption :return: A :class:`boto.vpc.customergateway.DhcpOption` object """

        params = {'VpcId' : vpc_id,
                  'CidrBlock' : cidr_block}
        if availability_zone:
            params['AvailabilityZone'] = availability_zone
        return self.get_object('CreateDhcpOption', params, DhcpOptions)