docs: def required(field):
      """Decorator that checks if return value is set, if not, raises exception.
      """
  
      def wrap(f):
          def wrappedf(*args):
              result = f(*args)
              if result is None or result == "":
                  raise Exception(
                      "Config option '%s' is required." % field)
              else:
                  return result
          return wrappedf
      return wrap