code: def config_to_string(config):
      
      output = []
      for section, section_content in config.items():
          output.append("[{}]".format(section))
          for option, option_value in section_content.items():
              output.append("{} = {}".format(option, option_value))
      return "\n".join(output)
docs: Nice output string for the config, which is a nested defaultdict.
  
      Args:
          config (defaultdict(defaultdict)): The configuration information.
      Returns:
          str: A human-readable output string detailing the contents of the config.