docs: def generate_sample_json():
      """Generate sample json data for testing"""
  
      check = EpubCheck(samples.EPUB3_VALID)
      with open(samples.RESULT_VALID, 'wb') as jsonfile:
          jsonfile.write(check._stdout)
  
      check = EpubCheck(samples.EPUB3_INVALID)
      with open(samples.RESULT_INVALID, 'wb') as jsonfile:
          jsonfile.write(check._stdout)