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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_standalone_app_url(self, app_id, spark_master_address, requests_config, tags):
 """ Return the application URL from the app info page on the Spark master. Due to a bug, we need to parse the HTML manually because we cannot fetch JSON data from HTTP interface. """

        app_page = self._rest_request(
            spark_master_address,
            SPARK_MASTER_APP_PATH,
            SPARK_STANDALONE_SERVICE_CHECK,
            requests_config,
            tags,
            appId=app_id,
        )

        dom = BeautifulSoup(app_page.text, 'html.parser')
        app_detail_ui_links = dom.find_all('a', string='Application Detail UI')

        if app_detail_ui_links and len(app_detail_ui_links) == 1:
            return app_detail_ui_links[0].attrs['href']