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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_vpn_gateway(self, type, availability_zone=None):
 """ Create a new Vpn Gateway :type type: str :param type: Type of VPN Connection. Only valid valid currently is 'ipsec.1' :type availability_zone: str :param availability_zone: The Availability Zone where you want the VPN gateway. :rtype: The newly created VpnGateway :return: A :class:`boto.vpc.vpngateway.VpnGateway` object """

        params = {'Type' : type}
        if availability_zone:
            params['AvailabilityZone'] = availability_zone
        return self.get_object('CreateVpnGateway', params, VpnGateway)