code: def _ray_posttask(self, key, result, pre_state):
      # Indicate the dask task is finished.
      self.pb.finish.remote(key, datetime.now())
  
imports: import contextlib
  from collections import namedtuple, defaultdict
  from datetime import datetime
  from dask.callbacks import Callback
label_desc: Use image node_id 4 for calling the ProgressBarCallback obj's underlying member method code with example usage: obj._ray_posttask(key, result, pre_state) without return types