code: @Override
      public AttachClassicLinkVpcResult attachClassicLinkVpc(AttachClassicLinkVpcRequest request) {
          request = beforeClientExecution(request);
          return executeAttachClassicLinkVpc(request);
      }
docs: <p>
  Links an EC2-Classic instance to a ClassicLink-enabled VPC through one or more of the VPC's security groups. You
  cannot link an EC2-Classic instance to more than one VPC at a time. You can only link an instance that's in the
  <code>running</code> state. An instance is automatically unlinked from a VPC when it's stopped - you can link it
  to the VPC again when you restart it.
  </p>
  <p>
  After you've linked an instance, you cannot change the VPC security groups that are associated with it. To change
  the security groups, you must first unlink the instance, and then link it again.
  </p>
  <p>
  Linking your instance to a VPC is sometimes referred to as <i>attaching</i> your instance.
  </p>
  
  @param attachClassicLinkVpcRequest
  @return Result of the AttachClassicLinkVpc operation returned by the service.
  @sample AmazonEC2.AttachClassicLinkVpc
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/ec2-2016-11-15/AttachClassicLinkVpc" target="_top">AWS API
  Documentation</a>