KeepReferenceAttribute
This attribute indicates the parameter will be referenced by the return
            object, hence its DS wrap object shouldn't be disposed even it is out
            of scope. The life-cycle of parameter will have the same life-cycle as
            the return object.
            
            Note the return object should be reference type.
            
using System;
namespace Autodesk.DesignScript.Runtime
{
    [AttributeUsage(AttributeTargets.Parameter)]
    public class KeepReferenceAttribute : Attribute
    {
    }
}
            