code: def reset_option(key):
      
      global _options
      if key == 'all':
          _options = copy.deepcopy(_original_options)
      else:
          if key not in _options.keys():
              raise KeyError('{key} not valid.'.format(key=key))
          _options[key] = _original_options[key]
docs: Reset one or more options to their default value.
  
      Pass "all" as argument to reset all options.
  
      Available options:
  
          parse.full_codestream
          print.xml
          print.codestream
          print.short
  
      Parameter
      ---------
      key : str
          Name of a single option.