code: def test_add_sn_hook(self):
      hook = SpectralNormalization(use_gamma=self.use_gamma)
      layer = self.layer
      layer.add_hook(hook)
      if self.lazy_init:
          assert not hasattr(layer, hook.vector_name)
          if self.use_gamma:
              assert not hasattr(layer, "gamma")
          with chainer.using_config("train", False):
              layer(self.x)
      assert hasattr(layer, hook.vector_name)
      assert (self.in_size,) == getattr(layer, hook.vector_name).shape
      if not self.use_gamma:
          assert not hasattr(layer, "gamma")
      else:  # Use gamma parameter
          assert hasattr(layer, "gamma")
          assert layer.gamma.ndim == 0 and layer.gamma.size == 1
  
imports: import copy
  import os
  import unittest
  import numpy
  import pytest
  import chainer
  from chainer.backends import _cpu
  from chainer.link_hooks.spectral_normalization import SpectralNormalization
  import chainer.links
  from chainer import serializers
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing.backend import BackendConfig
  from chainer import utils
label_desc: Use image node_id 2 for calling the TestEmbedID obj's underlying member method code with example usage: obj.test_add_sn_hook() without return types