Describe Customer Gateways Response from the service

You can filter the results to return information only about customer gateways that match criteria you specify. For example, you could ask to get information about a particular customer gateway (or all) only if the gateway's state is pending or available. You can specify multiple filters (e.g., the customer gateway has a particular IP address for the Internet-routable external interface, and the gateway's state is pending or available). The result includes information for a particular customer gateway only if the gateway matches all your filters. If there's no match, no special message is returned; the response is simply empty