Makes a request to combined url with `self._params` as parameters.
        If the server at combined url responds with Client or Server error, raises an exception.

        :return: the response from combined url
        :rtype: requests.models.Response

def fetch(self):
        """
        Makes a request to combined url with `self._params` as parameters.
        If the server at combined url responds with Client or Server error, raises an exception.

        :return: the response from combined url
        :rtype: requests.models.Response
        """
        response = self._session.get(self.url, params=self.params)
        response.raise_for_status()
        return response