code: def store_list(self, cb=None):
          
  
          from StringIO import StringIO
          import json
  
          d = {}
  
          for k, v in self.list().items():
  
              if 'caches' in v:
                  del v['caches']
  
              d[k] = v
  
          strio = StringIO(json.dumps(d))
  
          sink = self.put_stream('meta/_list.json')
  
          copy_file_or_flo(strio, sink, cb=cb)
          sink.close()
docs: List the cache and store it as metadata. This allows for getting the list from HTTP caches
          and other types where it is not possible to traverse the tree