def web_application_firewall_policies(self):
        """Instance depends on the API version:

           * 2018-12-01: :class:`WebApplicationFirewallPoliciesOperations<azure.mgmt.network.v2018_12_01.operations.WebApplicationFirewallPoliciesOperations>`
           * 2019-02-01: :class:`WebApplicationFirewallPoliciesOperations<azure.mgmt.network.v2019_02_01.operations.WebApplicationFirewallPoliciesOperations>`
        """
        api_version = self._get_api_version('web_application_firewall_policies')
        if api_version == '2018-12-01':
            from .v2018_12_01.operations import WebApplicationFirewallPoliciesOperations as OperationClass
        elif api_version == '2019-02-01':
            from .v2019_02_01.operations import WebApplicationFirewallPoliciesOperations as OperationClass
        else:
            raise NotImplementedError("APIVersion {} is not available".format(api_version))
        return OperationClass(self._client, self.config, Serializer(self._models_dict(api_version)), Deserializer(self._models_dict(api_version)))