docs: function (binding, cb) {
          if (!this.observedBindings) {
            this.observedBindings = [];
          }
  
          var bindingPath = binding.getPath();
          if (!Util.find(this.observedBindings, function (b) { return b.getPath() === bindingPath; })) {
            this.observedBindings.push(binding);
            setupObservedBindingListener(this, binding);
          }
  
          return cb ? cb(binding.get()) : undefined;
        }