this to the name of the attribute
       * or property. Hyphenated values are converted to camel case when used to
       * look up the property of a selectable element. Camel cased values are
       * *not* converted to hyphenated values for attribute lookup. It's
       * recommended that you provide the hyphenated form of the name so that
       * selection works in both cases. (Use `attr-or-property-name` instead of
       * `attrOrPropertyName`.)
       */
      attrForSelected: {
        type: String,