def to_python(self, value):
        if value in self.empty_values:
            return None
        if isinstance(value, datetime.timedelta):
            return value
        value = parse_duration(force_text(value))
        if value is None:
            raise ValidationError(self.error_messages['invalid'], code='invalid')
        return value
dataset/ETHPy150Open django/django/django/forms/fields.py/DurationField.to_python/original