def _service_request(self, request_type, sub_uri, params=None, callback=None,
                         raise_for_status=True, raw=False, **kwargs):
        """
        Base method for handling HTTP requests via the current requests session.
        :param request_type: The request type as a string (e.g. "POST", "GET", "PUT", etc.)
        :param sub_uri: The REST end point (sub-uri) to communicate with.
        :param params: (Optional) HTTP Request parameters. Default: none
        :param callback: (Optional) A callback function to be excuted on the resulting requests response.
                         This synchronous implementation will return the results of the callback.
                         Default: None. This method returns either the decoded JSON or the raw request content.
        :param raise_for_status: (Optional) When set True, we raise requests.HTTPError on 4xx or 5xx status. When
                                 set False, non-2xx/3xx status code is ignored. Default: True
        :param raw: (Optional) If no callback is set, return the raw content from the request if this is set True.
                    If False, the method attempts to parse the request as JSON data and return the resutls.
                    Default: False
        :param kwargs: Additional parameters to pass to the session request call.
        :return: The concurrent.futures object that holds the future for the API method call.
        """
        api_logger.debug("Sending request: {} ({})".format(sub_uri, request_type))
        if not self.session:
            self._start_http_session()
        uri = urljoin(self.uri_base, sub_uri)
        if params:
            kwargs.update(params=params)
        if callback:
            def base_callback(_, response):
                if raise_for_status:
                    response.raise_for_status()
                response.encoding = 'utf-8'
                return callback(response)
        else:
            def base_callback(_, response):
                if raise_for_status:
                    response.raise_for_status()
                response.encoding = 'utf-8'
                return response.content if raw else json.loads(response.text)
        response_future = self.session.request(request_type, uri, background_callback=base_callback, **kwargs)
        return response_future