Simplified version of PatternGenerator's __call__ method.

def _reduced_call(self, **params_to_override):
        """
        Simplified version of PatternGenerator's __call__ method.
        """
        p=param.ParamOverrides(self,params_to_override)

        fn_result = self.function(p)
        self._apply_mask(p,fn_result)
        result = p.scale*fn_result+p.offset
        return result