code: def _scope(self, flag):
      # If flag is None, return the nop context.
      # Otherwise, return the context in which
      # keep_graph_on_report is set temporarily.
      old = configuration.config.keep_graph_on_report
      if flag is not None:
          configuration.config.keep_graph_on_report = flag
      try:
          yield
      finally:
          configuration.config.keep_graph_on_report = old
  
imports: import contextlib
  import tempfile
  import threading
  import time
  import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import configuration
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import backend
label_desc: Use image node_id 1 for calling the TestKeepGraphOnReportFlag obj's underlying member method code with example usage: obj._scope(flag) without return types