code: def test_build_parallel(self):
      output = gokart.build(
          _ParallelRunner(), reset_register=False, workers=20
      )
      self.assertEqual(output, "done")
  
imports: import logging
  import os
  import unittest
  from copy import copy
  import luigi
  import luigi.mock
  import gokart
  from gokart.build import GokartBuildError, LoggerConfig
label_desc: Use image node_id 4 for calling the RunTest obj's underlying member method code with example usage: obj.test_build_parallel() without return types