The new 2-part objectives in OpenMx mean an older method for testing if a model is a RAM model don't work
I used to say this:
(isS4(obj) && is(obj, "MxModel") && class(obj$objective) == "MxRAMObjective")
What code do people recommend for backward (and preferably forward compatible testing of model type? Do we need to add a type= field to MXModel?