code: def formatter(name, default=False):
      
      def decorator(func):
          func._output_format = dict(name=name, default=default)
          return func
      return decorator
docs: Decorate a Feature method to register it as an output formatter.
  
      All formatters are picked up by the argument parser so that they can be
      listed and selected on the CLI via the -f, --format argument.