The XMI you are showing is the GMF notation model. It’s an EMF model just like the Capella model so you could access this information but the Python API is clearly not designed to to this.
In Java you can have a look at org.eclipse.gmf.runtime.notation.Node and the Node.getElement() should return a DDiagramElement from Sirius. Then you could check if the referenced element is your component. Capella provides a utility class ShapeUtil that might be interesting for you.