code: def _update_threads(self):
      for c in HANDLER_METHODS:
          tgt_parallelism = self._parallelism.get(c, 1)
          assert tgt_parallelism >= 0
          cur_parallelism = lambda: len(self.thread_groups[c])
  
          # Scale up threads if necessary
          while tgt_parallelism > cur_parallelism():
              in_queue = self.queues[c + "_in"]
              out_queue = self.queues[c + "_out"]
              call = getattr(self.handler, c)
              event = threading.Event()
  
              t = threading.Thread(
                  target=execute_call,
                  args=(
                      in_queue,
                      out_queue,
                      call,
                      self.thread_local_data,
                      event,
                  ),
              )
              t.start()
              self.thread_groups[c].append(WorkerThread(event, t))
  
          # Scale down threads if necessary
          while tgt_parallelism < cur_parallelism():
              self.thread_groups[c][-1].event.set()
              self.thread_groups[c][-1].thread.join()
              self.thread_groups[c].pop()
  
imports: import os
  import queue
  import threading
  import time
  from copy import copy
  from dataclasses import dataclass
  from typing import Dict
label_desc: Use image node_id 7 for calling the MicroBatching obj's underlying member method code with example usage: obj._update_threads() without return types