code: function() {
          if (get(this, 'isFrozen')) throw new EmberError(FROZEN_ERROR);
          var obj = this.length > 0 ? this[this.length-1] : null;
          this.remove(obj);
          return obj;
        }
docs: Removes the last element from the set and returns it, or `null` if it's empty.
  
  ```javascript
  var colors = new Ember.Set(["green", "blue"]);
  colors.pop();  // "blue"
  colors.pop();  // "green"
  colors.pop();  // null
  ```
  
  @method pop
  @return {Object} The removed object from the set or null.