def tokensetter(self, f):
self._tokensetter = f<EOL>return f<EOL>
Register a function to save the bearer token.

        The setter accepts two parameters at least, one is token,
        the other is request::

            @oauth.tokensetter
            def set_token(token, request, *args, **kwargs):
                save_token(token, request.client, request.user)

        The parameter token is a dict, that looks like::

            {
                u'access_token': u'6JwgO77PApxsFCU8Quz0pnL9s23016',
                u'token_type': u'Bearer',
                u'expires_in': 3600,
                u'scope': u'email address'
            }

        The request is an object, that contains an user object and a
        client object.