def _calculate(self, startingPercentage, endPercentage, startDate, endDate):
        # get the defined subset of error values
        errorValues = self._get_error_values(startingPercentage, endPercentage, startDate, endDate)

        return float(sum(errorValues)) / float(len(errorValues))
This is the error calculation function that gets called by :py:meth:`BaseErrorMeasure.get_error`.
dataset/ETHPy150Open T-002/pycast/pycast/errors/symmetricmeanabsolutepercentageerror.py/SymmetricMeanAbsolutePercentageError._calculate