code: function (fn, update, container) {
    // Alias passed in variables for later access.
    this._fn        = fn;
    this._update    = update;
    this._container = container;
  
    // Assign every subscription instance a unique id. This helps with linking
    // between parent and child subscription instances.
    this.cid             = 'c' + Utils.uniqueId();
    this.children        = {};
    this.subscriptions   = {};
    this.unsubscriptions = [];
  
    // Create statically bound function instances for public consumption.
    this.boundUpdate         = Utils.bind(this.update, this);
    this.boundUnsubscription = Utils.bind(this.unsubscription, this);
  }
docs: Create a new subsciption instance. This functionality is tightly coupled to
  DOMBars program execution.
  
  @param {Function} fn
  @param {Function} update
  @param {Object}   container