return Object.extend(destination, source); 
return Object.extend(destination.prototype, source); 
  mixin: function(destination, source) {    return Object.extend(destination, source);  }
4053	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/4053/b8ec17fb9a9503b3599947de79d66a077d483799/prototype.js/clean/lib/prototype.js