code: def test(self):
      # Assume ls command exists
      self.assertTrue(pfrl.utils.is_return_code_zero(["ls"]))
      self.assertFalse(
          pfrl.utils.is_return_code_zero(["ls --nonexistentoption"])
      )
      self.assertFalse(
          pfrl.utils.is_return_code_zero(["nonexistentcommand"])
      )
  
imports: import unittest
  import pfrl
label_desc: Use image node_id 1 for calling the TestIsReturnCodeZero obj's underlying member method code with example usage: obj.test() without return types