code: def on_epoch_end(self, training_state):
      for callback in self.callbacks:
          callback.on_epoch_end(training_state)
  
imports: from __future__ import division, print_function, absolute_import
  import time
  import sys
label_desc: Use image node_id 8 for calling the ChainCallback obj's underlying member method code with example usage: obj.on_epoch_end(training_state) without return types