Description:
Could you please provide an example of using an id_short path parameter in get_referable? This is related to #214.

Problem:
part01 = submodel.get_referable(('model01', 'part01'))
Where 'model01' is an SMC inside the submodel, and 'part01' is an SMC inside 'model01'.

Error:
KeyError: "Referable with id_short ('model01', 'part01') not found in this namespace"

Question:
What is the correct way of using an id_short path parameter?