code: def unset(config, section, opt=None):
          
          if section not in config.keys():
              raise ConfigError("section '{}' doesn't exist".format(section))
  
          if opt is None:
              del config[section]
              return
  
          if opt not in config[section].keys():
              raise ConfigError(
                  "option '{}.{}' doesn't exist".format(section, opt)
              )
          del config[section][opt]
  
          if not config[section]:
              del config[section]
docs: Unsets specified option and/or section in the config.
  
          Args:
              config (configobj.ConfigObj): config to work on.
              section (str): section name.
              opt (str): optional option name.