def save(self):
        tmp_path = self.path + '.tmp'
        with open(tmp_path, 'w') as f:
            f.write(json.dumps(self.body_labels.items()))
        os.rename(tmp_path, self.path)
def days_till_due(self):
        """
        Returns the number of days till the due date. Returns a negative number
        of days when the due date is in the past.
        Returns 0 when the task has no due date.
        """
        due = self.due_date()
        if due:
            diff = due - date.today()
            return diff.days
        return 0