code: def put_object_acl(self, bucket, object_name, access_control_policy):
          
          data = access_control_policy.to_xml()
          details = self._details(
              method=b"PUT",
              url_context=self._url_context(
                  bucket=bucket, object_name='%s?acl' % (object_name,),
              ),
              body=data,
          )
          query = self._query_factory(details)
          d = self._submit(query)
          d.addCallback(self._parse_acl)
          return d
docs: Set access control policy on an object.