@property
    def markdown_key(self):
        return 'article-%d-markdown' % self.id
unary operator
dataset/ETHPy150Open 2buntu/2buntu-blog/twobuntu/articles/models.py/Article.markdown_key--crossover with--dataset/ETHPy150Open xraypy/xraylarch/lib/interpreter.py/Interpreter.on_unaryop