_pushModifyObjectCommand(obj) {
    const { type } = obj;
    const props = makeSelectionUndoData(obj, (item) =>
      makeSelectionUndoDatum(this._graphics.getObjectId(item), item, type === 'activeSelection')
    );
    const command = commandFactory.create(commands.CHANGE_SELECTION, this._graphics, props);
    command.execute(this._graphics, props);

    this._invoker.pushUndoStack(command);
  }
Add a 'changeSelection' command
@param {fabric.Object} obj - selection object
@private