public function column_default( $item, $column_name ) {
		/**
		 * Fires inside each custom column of the Multisite themes list table.
		 *
		 * @since 3.1.0
		 *
		 * @param string   $column_name Name of the column.
		 * @param string   $stylesheet  Directory name of the theme.
		 * @param WP_Theme $theme       Current WP_Theme object.
		 */
		do_action(
			'manage_themes_custom_column',
			$column_name,
			$item->get_stylesheet(), // Directory name of the theme.
			$item // Theme object.
		);
	}