setTagName (tagName) { // eslint-disable-line no-unused-vars
    /* istanbul ignore next */
    throw new Error(NOT_IMPLEMENTED)
  }
Set the tagName of this element.

    @private
    @note Considered as private API, in favor of the property {DOMElement.prototype.tagName}
    @param {String} tagName the new tag name
    @returns {this}