docs: def _genpath(self, filename, mhash):
          """Generate the path to a file in the cache.
  
          Does not check to see if the file exists. Just constructs the path
          where it should be.
          """
          mhash = mhash.hexdigest()
          return os.path.join(self.mh_cachedir, mhash[0:2], mhash[2:4],
                              mhash, filename)