Create and save a new access token.

        Similar to OAuth 2, indication of granted scopes will be included as a
        space separated list in ``oauth_authorized_realms``.

        :param request: OAuthlib request.
        :type request: oauthlib.common.Request
        :returns: The token as an urlencoded string.

def create_access_token(self, request, credentials):
        """Create and save a new access token.

        Similar to OAuth 2, indication of granted scopes will be included as a
        space separated list in ``oauth_authorized_realms``.

        :param request: OAuthlib request.
        :type request: oauthlib.common.Request
        :returns: The token as an urlencoded string.
        """
        request.realms = self.request_validator.get_realms(
            request.resource_owner_key, request)
        token = {
            'oauth_token': self.token_generator(),
            'oauth_token_secret': self.token_generator(),
            # Backport the authorized scopes indication used in OAuth2
            'oauth_authorized_realms': ' '.join(request.realms)
        }
        token.update(credentials)
        self.request_validator.save_access_token(token, request)
        return urlencode(token.items())