def verifiergetter(self, f):
self._verifiergetter = f<EOL>return f<EOL>
Register a function as the verifier getter.

        The return verifier object should at least contain a user object
        which is the current user.

        The implemented code looks like::

            @oauth.verifiergetter
            def load_verifier(verifier, token):
                data = Verifier.get(verifier)
                if data.request_token == token:
                    # check verifier for safety
                    return data
                return data