code: @Override
      public AttachVpnGatewayResult attachVpnGateway(AttachVpnGatewayRequest request) {
          request = beforeClientExecution(request);
          return executeAttachVpnGateway(request);
      }
docs: <p>
  Attaches a virtual private gateway to a VPC. You can attach one virtual private gateway to one VPC at a time.
  </p>
  <p>
  For more information, see <a href="https://docs.aws.amazon.com/vpn/latest/s2svpn/VPC_VPN.html">AWS Site-to-Site
  VPN</a> in the <i>AWS Site-to-Site VPN User Guide</i>.
  </p>
  
  @param attachVpnGatewayRequest
  Contains the parameters for AttachVpnGateway.
  @return Result of the AttachVpnGateway operation returned by the service.
  @sample AmazonEC2.AttachVpnGateway
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/ec2-2016-11-15/AttachVpnGateway" target="_top">AWS API
  Documentation</a>