code: def test_basic(self):
      self.optimizer.x = 0
      extension = extensions.MultistepShift(
          "x", self.gamma, self.step_value, self.init, self.optimizer
      )
      self._run_trainer(extension, self.expect)
  
file_path: chainer/tests/chainer_tests/training_tests/extensions_tests/test_multistep_shift.py
imports: import unittest
  import mock
  from chainer import testing
  from chainer.training import extensions
  from chainer.training import util
label_desc: Use image node_id 3 for calling the TestMutistepShift obj's underlying member method code with example usage: obj.test_basic() without return types