def explanation(self):
        min_unit = None
        for question in self.question.answers:
            normalized = convert.to_normalized(question.unit, 1)
            if min_unit is None or convert.to_normalized(min_unit, 1) > normalized:
                min_unit = question.unit

        if min_unit and min_unit != self.unit:
            converted_value = convert.convert(self.unit, self.value, min_unit)
            if converted_value.magnitude > 0.001:
                return convert.format_quantity(converted_value)
            else:
                # the value is below the required precision so we cannot use it
                return None
        else:
            return None
 def normalized_value(self):
     return convert.to_normalized(self.unit, self.value)