def add_fast(self, filepath, hashfn=None, force=False):
        """
        Bespoke function to add filepaths but set shortcircuit to True, which
        means only the first calculable hash will be stored. In this way only
        one "fast" hashing function need be called for each filepath.
        """
        if hashfn is None:
            hashfn = fast_hashes
        self.add(filepath, hashfn, force, shortcircuit=True)
Bespoke function to add filepaths but set shortcircuit to True, which
        means only the first calculable hash will be stored. In this way only
        one "fast" hashing function need be called for each filepath.