python mixin

mixin有2个使用原则：
1. 如果你想给一个类附加很多可选的方法和属性
2. 有很多类使用同一个特定的方法和属性
一个比较好的在类的方法里添加日志的mixin

class LoggingMixin(object):
    """
    Convenience super-class to have a logger configured with the class name
    """
    def __init__(self, context=None):
        if context is not None:
            set_context(self.log, context)

    # We want to deprecate the logger property in Airflow 2.0
    # The log property is the de facto standard in most programming languages
    @property
    def logger(self):
        warnings.warn(
            'Initializing logger for {} using logger(), which will '
            'be replaced by .log in Airflow 2.0'.format(
                self.__class__.__module__ + '.' + self.__class__.__name__
            ),
            DeprecationWarning
        )
        return self.log

    @property
    def log(self):
        try:
            return self._log
        except AttributeError:
            self._log = logging.root.getChild(
                self.__class__.__module__ + '.' + self.__class__.__name__
            )
            return self._log