def METHOD_NAME(self):
    """Return a separate copy of this hashing object.
    An update to this copy won't affect the original object.
    """
    other = self.__class__(_secret_backdoor_key)
    other.digest_cons = self.digest_cons
    other.digest_size = self.digest_size
    other.inner = self.inner.METHOD_NAME()
    other.outer = self.outer.METHOD_NAME()
    return other