code: def test_single_no_show_gpu(self):
      times = numpy.array([[5.4], [6.4]]) * 1e-6
      perf = cupyx.time._PerfCaseResult("test_name_xxx", times, (0,))
      assert (
          perf.to_str() == "test_name_xxx       :    CPU:     5.400 us"
      )
  
file_path: cupy/tests/cupyx_tests/test_time.py
imports: import unittest
  from unittest import mock
  import numpy
  import cupy
  from cupy import testing
  import cupyx
label_desc: Use image node_id 4 for calling the TestPerfCaseResult obj's underlying member method code with example usage: obj.test_single_no_show_gpu() without return types