ZNB don't snapshot traces

[jenshnielsen]

They are slow and may not even function correctly if the trigger is not set and there is no point of snapshotting array parameters

[jenshnielsen]

@WilliamHPNielsen

[AdriaanRol]

@jenshnielsen , I feel that this is a problem that is bound to occur more frequently. Rather than overwritting the snapshot method, would it not be better to add this as a property of the parameter that is set through the add_parameter method. Something like include_in_snapshot=True/False ?

[jenshnielsen]

Perhaps, but that API does not exist and this one does because of special handling in https://github.com/QCoDeS/Qcodes/blob/master/qcodes/instrument_drivers/QDev/QDac_channels.py#L107 that cannot be done with a bool as the point is to intersept the snapshot and call an alternative method the bulk updates all the parameters in one instrument call.

I will prefer not touch the parameters until #600 lands. Honestly I think we will get a long way by excluding Array and Multiparameters per default there is almost never any good reason to snapshot those.

[WilliamHPNielsen]

That's how it should be.

[jenshnielsen]

I added #759 to remind us to improve this in general