We already do something like this for PowerSpectrum: we have a _convert_power_function() routine that we run when initializing the PowerSpectrum object, that checks that it can get the power at certain values of k.  The outputs of that conversion routine are not saved at that time, so the sole reason for running it when initializing is to immediately give the user feedback that their power function may be invalid.  I suggest doing something like that here, as well.