def clear(self, youngest_rev=None):
        self.youngest = None
        if youngest_rev is not None:
            self.youngest = self.normalize_rev(youngest_rev)
        self.oldest = None
Reset notion of `youngest` and `oldest`
dataset/ETHPy150Open edgewall/trac/tracopt/versioncontrol/svn/svn_fs.py/SubversionRepository.clear