_WP_List_Table_Compat::__construct( $screen,  $columns = array() )

	public function __construct( $screen, $columns = array() ) {
		if ( is_string( $screen ) )
			$screen = convert_to_screen( $screen );

		$this->_screen = $screen;

		if ( !empty( $columns ) ) {
			$this->_columns = $columns;
			add_filter( 'manage_' . $screen->id . '_columns', array( $this, 'get_columns' ), 0 );
		}
	}