code: def _check_context(ctx):
      try:
          x = nn.Variable()
          F.relu(x)
      except:
          logger.warning("Fallback to CPU context.")
          import nnabla_ext.cpu
  
          ctx = nnabla_ext.cpu.context()
      return ctx
  
imports: import itertools
  import os
  import re
  from collections import OrderedDict
  import nnabla
  import nnabla.functions
  import nnabla.solver
  import numpy
  from nnabla.core.graph_optimizer import IdentityRemover
  from nnabla.initializer import NormalInitializer, UniformInitializer, ConstantInitializer, RangeInitializer
  from nnabla.logger import logger
  from nnabla.utils import nnabla_pb2
  from nnabla.utils.communicator_util import current_communicator, single_or_rankzero
  from nnabla.utils.create_cache import CreateCache
  from nnabla.utils.data_iterator import data_iterator_csv_dataset, data_iterator_cache
  from nnabla.utils.get_file_handle import get_initial_file_loader, load_files
  from nnabla.utils.learning_rate_scheduler import PolynomialScheduler, CosineScheduler, ExponentialScheduler, StepScheduler, LinearWarmupScheduler
label_desc: Use image node_id 4 for calling a global function with example usage: _check_context(ctx) and returns: ctx