code: def load_roberta(self):
      os.makedirs(local_path, exist_ok=True)
      model_url = data_url + "/analytics-zoo-data/roberta.tar"
      model_path = maybe_download("roberta.tar", local_path, model_url)
      tar = tarfile.open(model_path)
      tar.extractall(path=local_path)
      tar.close()
      model_path = os.path.join(local_path, "roberta/model.xml")
      self.est = Estimator.from_openvino(model_path=model_path)
  
imports: import os
  import tarfile
  import tempfile
  import shutil
  from unittest import TestCase
  import numpy
  from bigdl.dllib.feature.dataset.base import maybe_download
  from bigdl.dllib.nncontext import init_nncontext
  from bigdl.orca.data import SparkXShards
  from bigdl.orca.learn.openvino import Estimator
label_desc: Use image node_id 5 for calling the TestEstimatorForOpenVINO obj's underlying member method code with example usage: obj.load_roberta() without return types