code: def scan_elements(self):
          
          for x in self.redis.sscan_iter(self.key):
              yield self._unpickle(x)
docs: Yield each of the elements from the collection, without pulling them
          all into memory.
  
          .. warning::
              This method is not available on the set collections provided
              by Python.
  
              This method may return the element multiple times.
              See the `Redis SCAN documentation
              <http://redis.io/commands/scan#scan-guarantees>`_ for details.