def _build_url(self, path=None):
        """
        helper function to build a WFS 3.0 URL

        @type path: string
        @param path: path of WFS URL

        @returns: fully constructed URL path
        """

        url = self.url
        if self.url_query_string is not None:
            LOGGER.debug('base URL has a query string')
            url = urljoin(url, path)
            url = '?'.join([url, self.url_query_string])
        else:
            url = urljoin(url, path)

        LOGGER.debug('URL: {}'.format(url))
        return url
helper function to build a WFS 3.0 URL

        @type path: string
        @param path: path of WFS URL

        @returns: fully constructed URL path