code: def testCheckPipelineExistenceRequired(self):
      flags_dict = {
          labels.ENGINE_FLAG: "beam",
          labels.PIPELINE_NAME: "chicago_taxi_beam",
      }
      handler = FakeHandler(flags_dict)
      with self.assertRaises(SystemExit) as err:
          handler._check_pipeline_existence(
              flags_dict[labels.PIPELINE_NAME]
          )
      self.assertTrue(
          str(err.exception),
          'Pipeline "{}" does not exist.'.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 6 for calling the BaseHandlerTest obj's underlying member method code with example usage: obj.testCheckPipelineExistenceRequired() without return types