code: def read(self):
          
  
          def warn(msg, elapsed_time, current_time):
              desc = self._cache_id_desc()
              self._warnings(
                  "{0} {1}: {2}s < {3}s", msg, desc, elapsed_time, current_time)
  
          file_time = get_time()
          out = self._out
          if out is None:
              if self.verbose:
                  self._warnings("reading {0} from disk", self._cache_id_desc())
              with open(self._cache_file, 'rb') as f_in:
                  out = None
                  while True:
                      t_out = f_in.read(CHUNK_SIZE)
                      if not len(t_out):
                          break
                      if out is not None:
                          out += t_out
                      else:
                          out = t_out
                  self._out = out
          (cache_id_obj, elapsed_time, res) = self._read(out)
          self.ensure_cache_id(cache_id_obj)
          real_time = get_time() - file_time
          if elapsed_time is not None and real_time > elapsed_time:
              warn("reading cache from disk takes longer than computing!",
                   elapsed_time, real_time)
          elif self._start_time is not None and elapsed_time is not None:
              current_time = get_time() - self._start_time
              if elapsed_time < current_time:
                  warn("reading cache takes longer than computing!",
                       elapsed_time, current_time)
          self._last_access = get_time()
          return res
docs: Reads the cache file as pickle file.