code: def test_basic(self):
      self.optimizer.x = 0
      extension = extensions.WarmupShift(
          "x",
          self.warmup_start,
          self.warmup_iter,
          self.init,
          self.optimizer,
      )
      self._run_trainer(extension, self.expect)
  
file_path: chainer/tests/chainer_tests/training_tests/extensions_tests/test_warmup_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 TestWarmupShift obj's underlying member method code with example usage: obj.test_basic() without return types