code: def is_changed(self, target, previous_params):
      target_params = list(sorted(target.namedparams()))
      if len(previous_params) != len(target_params):
          return True
  
      for param1, param2 in zip(target_params, previous_params):
          name1, var1 = param1
          name2, var2 = param2
          if (name1 != name2) or (var1.data is None) != (
              var2.data is None
          ):
              return True
      return False
  
imports: import chainer
  import copy
label_desc: Use image node_id 4 for calling the _DoubleBufferingOptimizer obj's underlying member method code with example usage: obj.is_changed(target, previous_params) and returns: False, True, True