code: def pool(self):
          
          if self._pool is None:
              processes = self.processes
              if processes is not None and processes < 0:
                  try:
                      # cpu count includes the hyperthreads, e.g. 8 for 4 cores + hyperthreading
                      processes = multiprocessing.cpu_count() - abs(processes)
                      processes = max(processes, 1)
                  except (ImportError, NotImplementedError):
                      processes = None
  
              self._pool = multiprocessing.Pool(processes,
                                                initializer=_Pool_initialize_worker,
                                                initargs=(self.augseq, self.seed),
                                                maxtasksperchild=self.maxtasksperchild)
          return self._pool
docs: Return the multiprocessing.Pool instance or create it if not done yet.
  
          Returns
          -------
          multiprocessing.Pool
              The multiprocessing.Pool used internally by this imgaug.multicore.Pool.