Typelibrary should support typed data classes

[gordonwatts]

In this query we first create a dictionary. It would be nice to do this in a dataclass that was typed.

query = (ds
         .Select(lambda e: {
             'evt': e.EventInfo("EventInfo"),
             'jet': e.Jets()
             })
         .Select(lambda ei: {
             'event_number': ei.evt.eventNumber(),
             'run_number': ei.evt.runNumber(),
             'jet_pt': ei.jet.Select(lambda j: j.pt()/1000),
             'jet_energy_sampling': ei.jet.Select(lambda j: j.getAttribute[cpp_vfloat]("EnergyPerSampling")),
         })
)