Obtain the useful state of this credentials object so that
        we can reconstruct it independently.

def state(self):
        """Obtain the useful state of this credentials object so that
        we can reconstruct it independently.
        """
        return dict(
            (attr, getattr(self, attr))
            for attr in (
                'consumer_key', 'consumer_secret', 'callback_uri',
                'verified', 'oauth_token', 'oauth_token_secret',
                'oauth_session_handle', 'oauth_expires_at',
                'oauth_authorization_expires_at', 'scope'
            )
            if getattr(self, attr) is not None
        )