code: function(instance, objects) {
      var self = this;
      var after = this.afterRemovingObjects.bind(this, instance, objects);
      var removable = _.filter(objects, 'persisted');
      return self._updateForeignKeys(instance, removable, undefined).tap(after);
    }
docs: Perform the necessary updates to remove objects for this relation.
  
  This method invalidates the {@link HasMany#objectsQuery}.
  
  Mixins can override {@link HasMany#executeRemove} to change the way
  updates are performed when related objects are removed. This is the
  default implementation.
  
  @method
  @protected
  @param {Model} instance The model instance on which to operate.
  @param {Array} objects The objects to remove from the relationship.