docs: def upload_object(self, container, obj, contents,
                        content_length=None, metadata=None, **kwargs):
          """Upload object
  
          :param container: container name (Container is equivalent to
                            Bucket term in Amazon).
          :param obj: object name (Object is equivalent to
                      Key term in Amazon).
          :param contents: object content.
          :param content_length(int): content length.
          :param metadata (dict): addition infomation.
          :param **kwargs(dict): extend args for specific driver.
          """
          try:
              LOG.debug('upload_object() with %s is success.', self.driver)
              return self.driver.upload_object(container, obj,
                                               contents=contents,
                                               content_length=content_length,
                                               metadata=metadata,
                                               **kwargs)
          except DriverException as e:
              LOG.exception('upload_object() with %s raised\
                              an exception %s.', self.driver, e)