'We don\'t store the timestamp when pickling, to avoid the hash
depending from it.
In addition, when unpickling, we run the __init__'

def __reduce__(self):

    cachedir = (self.cachedir[:(-7)] if (self.cachedir is not None) else None)
    return (self.__class__, (cachedir, self.mmap_mode, self.compress, self._verbose))
