code: def _assertFileExists(self, path):
      self.assertTrue(fileio.exists(path), f"{path} does not exist.")
  
imports: import os
  import subprocess
  from absl.testing import parameterized
  import tensorflow
  from tfx.dsl.io import fileio
  from tfx.examples.penguin import penguin_pipeline_local_infraval
  from tfx.orchestration import metadata
  from tfx.orchestration.local.local_dag_runner import LocalDagRunner
  from tfx.utils import path_utils
  from ml_metadata.proto import metadata_store_pb2
label_desc: Use image node_id 2 for calling the PenguinPipelineLocalInfravalEndToEndTest obj's underlying member method code with example usage: obj._assertFileExists(path) without return types