code: def optional_tuning_records(log_filename):
      """Returns existing tuning records, if any."""
      if log_filename == "" or not os.path.exists(log_filename):
          return tvm.autotvm.task.FallbackContext()
      else:
          return tvm.autotvm.task.ApplyHistoryBest(log_filename)
  
imports: import tvm
  import logging
  import tempfile
  import os
  import shutil
  import numpy
  from tvm.relay import testing
  from tvm import rpc
  from tvm.contrib import utils, ndk
  from tvm.relay.build_module import bind_params_by_name
  from tvm.relay.collage.collage import *
  from tvm.relay.op.contrib import clml
  import pytest
label_desc: Use image node_id 2 for calling a global function with example usage: optional_tuning_records(log_filename) and returns: tvm, tvm