Construct geocoding request url. Overridden.

        :param str base_api: Geocoding function base address - self.api
            or self.reverse_api.

        :param dict params: Geocoding params.

        :return: string URL.

def _construct_url(self, base_api, params):
        """
        Construct geocoding request url. Overridden.

        :param str base_api: Geocoding function base address - self.api
            or self.reverse_api.

        :param dict params: Geocoding params.

        :return: string URL.
        """
        params['key'] = self.api_key
        return super(PickPoint, self)._construct_url(base_api, params)