Feature Request: determine if a reactive object is observed by any Vue instance

I would like to request a new feature. I want to determine if a reactive object is observed by any Vue instances.

Example:

var obj1 = {name: 'obj1'};
var obj2 = {name: 'obj2'};

var app = new Vue({
  el: '#app',
  data: {
    item: {}
  },
  mounted: function onMounted(){
    this.item = obj1;
    this.item = obj2;
  },
  methods: {
    pickItem: function pickItem() {
    	this.item = items[this.pickedElemId];
    }
  }
});

I want to determine if obj1 is observed by any Vue instances. In this example it is clear that the obj2 is observed but obj1 is not.

The reasons behind this feature request is discussed in this issue: https://github.com/vuejs/vue/issues/4384

[fnlctrl]

You can already check it now using the (private) __ob__ property.

if (obj.__ob__) { /*It's observed by vue*/ }

Though I don’t know if it’s worth adding a public API for it. Maybe __ob__ is good enough (at least for 2.x)?

[kailniris]

The pattern discussed in this (https://github.com/vuejs/vue/issues/4384) issue is a suitable workaround for the problem so this feature request is unnecessary.