code: def change_object_content_type(self, container, obj, new_ctype,
              guess=False, extra_info=None):
          
          return self._manager.change_object_content_type(container, obj,
                  new_ctype, guess=guess)
docs: Copies object to itself, but applies a new content-type. The guess
          feature requires the container to be CDN-enabled. If not then the
          content-type must be supplied. If using guess with a CDN-enabled
          container, new_ctype can be set to None. Failure during the put will
          result in a swift exception.
  
          The 'extra_info' parameter is included for backwards compatibility. It
          is no longer used at all, and will not be modified with swiftclient
          info, since swiftclient is not used any more.