Merge a pull request.
        :param request_id: the id of the request
        :return:

def merge_request(self, request_id):
        """
        Merge a pull request.
        :param request_id: the id of the request
        :return:
        """
        request_url = "{}pull-request/{}/merge".format(self.create_basic_url(),
                                                       request_id)

        return_value = self._call_api(request_url, method='POST')

        LOG.debug(return_value)