code: def prepare(self, dirname="test", device=None):
      outdir = os.path.join(self.temp_dir, dirname)
      self.updater = training.updaters.StandardUpdater(
          self.iterator, self.optimizer, device=device
      )
      self.trainer = training.Trainer(
          self.updater, (self.n_epochs, "epoch"), out=outdir
      )
      self.trainer.extend(training.extensions.FailOnNonNumber())
  
imports: import os
  import shutil
  import tempfile
  import unittest
  import warnings
  import numpy
  import chainer
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
  from chainer import training
label_desc: Use image node_id 3 for calling the TestFailOnNonNumber obj's underlying member method code with example usage: obj.prepare(dirname, device) without return types