public function sortables( array $cols ) : array {

		foreach ( $this->args['admin_cols'] as $id => $col ) {
			if ( ! is_array( $col ) ) {
				continue;
			}
			if ( isset( $col['sortable'] ) && ! $col['sortable'] ) {
				continue;
			}
			if ( isset( $col['meta_key'] ) || isset( $col['taxonomy'] ) || isset( $col['post_field'] ) ) {
				$cols[ $id ] = $id;
			}
		}

		return $cols;

	}