If building a PVsystem from PVcell, PVmodule, and PVstring instances, there is an option for the user to set pvconst each time. If the user does not set the kwarg, the instance of that class defaults to the default PVConstant() instance. This is confusing. For instance, if it set npts=1001 in my creation of my PVcell object, and then pass that object to my PVmodule instantiation and then my PVsystem instantiation, I would expect npts to propogate, but it does not.