code: def testCheckPipelinExistenceNotRequired(self):
      flags_dict = {
          labels.ENGINE_FLAG: "beam",
          labels.PIPELINE_NAME: "pipeline",
      }
      handler = FakeHandler(flags_dict)
      fileio.makedirs(
          os.path.join(
              os.environ["HOME"], "tfx", "beam", "pipeline", ""
          )
      )
      with self.assertRaises(SystemExit) as err:
          handler._check_pipeline_existence(
              flags_dict[labels.PIPELINE_NAME], required=False
          )
      self.assertTrue(
          str(err.exception),
          'Pipeline "{}" already exists.'.format(
              flags_dict[labels.PIPELINE_NAME]
          ),
      )
  
imports: import os
  import textwrap
  import tensorflow
  from tfx.dsl.io import fileio
  from tfx.tools.cli import labels
  from tfx.tools.cli.handler import base_handler
label_desc: Use image node_id 5 for calling the BaseHandlerTest obj's underlying member method code with example usage: obj.testCheckPipelinExistenceNotRequired() without return types