def get_available_units(self):
        """
        Uses the Verisign to fetch the number of available units left. This can be used to get tabs
        on the number of certificates that can be issued.

        :return:
        """
        url = current_app.config.get("VERISIGN_URL") + "/rest/services/getTokens"
        response = self.session.post(
            url, headers={"content-type": "application/x-www-form-urlencoded"}
        )
        return handle_response(response.content)["Response"]["Order"]

        Uses the Verisign to fetch the number of available units left. This can be used to get tabs
        on the number of certificates that can be issued.

        :return:
        
lemur/plugins/lemur_verisign/plugin.py