def _withCacheness(meth):
        """
        This is a paranoid test wrapper, that calls C{meth} 2 times, clear the
        cache, and calls it 2 other times. It's supposed to ensure that the
        plugin system behaves correctly no matter what the state of the cache
        is.
        """
        @functools.wraps(meth)
        def wrapped(self):
            meth(self)
            meth(self)
            self._clearCache()
            meth(self)
            meth(self)

        return wrapped

        This is a paranoid test wrapper, that calls C{meth} 2 times, clear the
        cache, and calls it 2 other times. It's supposed to ensure that the
        plugin system behaves correctly no matter what the state of the cache
        is.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_plugin.py