code: def hcompress(self, hashroot):
          
          hfiles = self.keys(hashroot + "/*")
          all = {}
          for f in hfiles:
              # print "using",f
              all.update(self[f])
              self.uncache(f)
  
          self[hashroot + '/xx'] = all
          for f in hfiles:
              p = self.root / f
              if p.name == 'xx':
                  continue
              p.unlink()
docs: Compress category 'hashroot', so hset is fast again
  
          hget will fail if fast_only is True for compressed items (that were
          hset before hcompress).