Specify the role of the new instance group (core, task).

C# |
[ObsoleteAttribute("The With methods are obsolete and will be removed in version 2 of the AWS SDK for .NET. See http://aws.amazon.com/sdkfornet/#version2 for more information.")] public AddInstanceGroup WithInstanceGroup( string instanceGroup )

- instanceGroup (String)
- New instance group's role.

A reference to this updated object so that method calls can be chained
together.