:param method: http request method
        :param url: http request url
        :param query_params: query parameters in the url
        :param headers: http request headers
        :param body: request json body, for `application/json`
        :param post_params: request post parameters,
                            `application/x-www-form-urlencode`
                            and `multipart/form-data`

def request(self, method, url, query_params=None, headers=None,
                body=None, post_params=None):
        """
        :param method: http request method
        :param url: http request url
        :param query_params: query parameters in the url
        :param headers: http request headers
        :param body: request json body, for `application/json`
        :param post_params: request post parameters,
                            `application/x-www-form-urlencode`
                            and `multipart/form-data`
        """
        method = method.upper()
        assert method in ['GET', 'HEAD', 'DELETE', 'POST', 'PUT', 'PATCH', 'OPTIONS']

        if post_params and body:
            raise ValueError(
                "body parameter cannot be used with post_params parameter."
            )

        post_params = post_params or {}
        headers = headers or {}

        if 'Content-Type' not in headers:
            headers['Content-Type'] = 'application/json'

        try:
            # For `POST`, `PUT`, `PATCH`, `OPTIONS`, `DELETE`
            if method in ['POST', 'PUT', 'PATCH', 'OPTIONS', 'DELETE']:
                if query_params:
                    url += '?' + urlencode(query_params)
                if headers['Content-Type'] == 'application/json':
                    request_body = None
                    if body is not None:
                        request_body = json.dumps(body)
                    r = self.pool_manager.request(method, url,
                                                  body=request_body,
                                                  headers=headers)
                if headers['Content-Type'] == 'application/x-www-form-urlencoded':
                    r = self.pool_manager.request(method, url,
                                                  fields=post_params,
                                                  encode_multipart=False,
                                                  headers=headers)
                if headers['Content-Type'] == 'multipart/form-data':
                    # must del headers['Content-Type'], or the correct Content-Type
                    # which generated by urllib3 will be overwritten.
                    del headers['Content-Type']
                    r = self.pool_manager.request(method, url,
                                                  fields=post_params,
                                                  encode_multipart=True,
                                                  headers=headers)
            # For `GET`, `HEAD`
            else:
                r = self.pool_manager.request(method, url,
                                              fields=query_params,
                                              headers=headers,
                                              preload_content=False)

        except urllib3.exceptions.SSLError as e:
            msg = "{0}\n{1}".format(type(e).__name__, str(e))
            raise ApiException(status=0, reason=msg)

        r = RESTResponse(r, method)

        # log response body
        logger.debug("response body: %s" % r.data)

        if r.status not in range(200, 206):
            raise ApiException(http_resp=r)

        return r