code: def add(self, callback):
      if not isinstance(callback, Callback):
          raise Exception(
              str(callback) + " is an invalid Callback object"
          )
  
      self.callbacks.append(callback)
  
imports: from __future__ import division, print_function, absolute_import
  import time
  import sys
label_desc: Use image node_id 10 for calling the ChainCallback obj's underlying member method code with example usage: obj.add(callback) without return types