code: @Override
      public ListGatewayGroupsResult listGatewayGroups(ListGatewayGroupsRequest request) {
          request = beforeClientExecution(request);
          return executeListGatewayGroups(request);
      }
docs: <p>
  Retrieves a list of gateway group summaries. Use GetGatewayGroup to retrieve details of a specific gateway group.
  </p>
  
  @param listGatewayGroupsRequest
  @return Result of the ListGatewayGroups operation returned by the service.
  @sample AmazonAlexaForBusiness.ListGatewayGroups
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/alexaforbusiness-2017-11-09/ListGatewayGroups"
  target="_top">AWS API Documentation</a>