code: function( isClosable ) {
  		this._canDestroy = isClosable || this.tabs.length > 1;
  		if( this.closeButton && this._isClosable() ) {
  			this.closeButton.element[ isClosable ? "show" : "hide" ]();
  			return true;
  		}
  
  		return false;
  	}
docs: Programmatically set closability.
  
  @package private
  @param {Boolean} isClosable Whether to enable/disable closability.
  
  @returns {Boolean} Whether the action was successful