code: def __call__(self, rule, param):
      p, g = param.data, param.grad
      if p is None or g is None:
          return
      self.value = np.copy(p)
  
imports: import pickle
  import unittest
  import numpy
  import six
  import chainer
  from chainer import functions
  from chainer import optimizers
  from chainer import testing
label_desc: Use image node_id 2 for calling the WeightSaveHook obj's underlying member method code with example usage: obj.__call__(rule, param) without return types