def validate(self, signed_value, max_age=None):
        """Just validates the given signed value.  Returns `True` if the
        signature exists and is valid, `False` otherwise."""
        try:
            self.unsign(signed_value, max_age=max_age)
            return True
        except BadSignature:
            return False
Just validates the given signed value.  Returns `True` if the
        signature exists and is valid, `False` otherwise.