code: function getUnusedDependencies(config) {
    return when(config.deps.reduce(updateIndex, clone(config.bundle)));
  
    function updateIndex(unused, dependency) {
      var location = dependency.getPathToBundle();
      if (location in unused) {
        delete unused[location];
      }
      return unused;
    }
  
    function clone(value) {
      return JSON.parse(JSON.stringify(value));
    }
  }
docs: implementation