function extendPrototype(sources, destination) {
  var i, len = sources.length, sourcePrototype;
  for (i = 0; i < len; i += 1) {
    sourcePrototype = sources[i].prototype;
    for (var attr in sourcePrototype) {
      if (sourcePrototype.hasOwnProperty(attr)) destination.prototype[attr] = sourcePrototype[attr];
    }
  }
}

function getDescriptor(object, prop) {
  return Object.getOwnPropertyDescriptor(object, prop);
}

function createProxyFunction(prototype) {
  function ProxyFunction() {}
  ProxyFunction.prototype = prototype;
  return ProxyFunction;
}