code: def option(value, is_default=False, label=None):
      
      _annotate("option", value, is_default=is_default, label=label)
docs: Annotates a possible value for IValueOptions,
      will be validated at instance creation time.
  
      @param value:      a possible value for the IValueOptions being defined.
      @type  value:      Any
      @param is_default: if the option should be the default value.
      @type  is_default: bool
      @param label:      option label or None; if none the string representation
                         of the value will be used as label.
      @type  label:      str or unicode or None