def _derX(self, w, x, y, z):
    '\n        Interpolated function w-derivative evaluator, to be defined in subclasses.\n        '
    raise NotImplementedError()
Interpolated function w-derivative evaluator, to be defined in subclasses.
def _derX(self, w, x, y, z):
    '\n        \n        '
    raise NotImplementedError()