Get from a CompartmentShape to the underlying class it is modelling

See more:

C#

DSL

I have a project that has a domain specific language (Microsoft.VisualStudio.Modelling) that uses the modelling SDK.

In that model I want my model shape to perform a function on the underlying class e.g. my diagram model is like:-

using DslModeling = global::Microsoft.VisualStudio.Modeling;
using DslDesign = global::Microsoft.VisualStudio.Modeling.Design;
using DslDiagrams = global::Microsoft.VisualStudio.Modeling.Diagrams;

public abstract partial class EventDefinitionCompartmentShapeBase : DslDiagrams::CompartmentShape
    {
       // auto code generated stuff
    }

This compartment shape is based off a domain class:-

public partial class EventDefinition : DslModeling::ModelElement
    {
    }

How would I get the instance of that class being modelled by the compartment shape code from within that compartment shape code?