docs: function readonly( target, attribs ) {
      const attribNames = Object.keys( attribs );
      attribNames.forEach( function ( attName ) {
          const attValue = attribs[ attName ];
          if ( typeof attValue === 'function' ) {
              Object.defineProperty(
                  target,
                  attName, {
                      set() {
                          throw Error( `Attribute "${attName}" is read only!` );
                      },
                      get: attValue,
                      configurable: false,
                      enumerable: true
                  }
              );
          } else {
              Object.defineProperty(
                  target,
                  attName, {
                      value: attValue,
                      writable: false,
                      configurable: false,
                      enumerable: true
                  }
              );
          }
      } );
  }