is_preset example

// Generate the pieces needed for rendering a duotone to the page.         if ( $has_duotone_attribute ) {

            /* * Possible values for duotone attribute: * 1. Array of colors - e.g. array('#000000', '#ffffff'). * 2. Variable for an existing Duotone preset - e.g. 'var:preset|duotone|blue-orange' or 'var(--wp--preset--duotone--blue-orange)'' * 3. A CSS string - e.g. 'unset' to remove globally applied duotone. */

            $duotone_attr = $block['attrs']['style']['color']['duotone'];
            $is_preset    = is_string( $duotone_attr ) && self::is_preset( $duotone_attr );
            $is_css       = is_string( $duotone_attr ) && ! $is_preset;
            $is_custom    = is_array( $duotone_attr );

            if ( $is_preset ) {

                $slug         = self::get_slug_from_attribute( $duotone_attr ); // e.g. 'blue-orange'.                 $filter_id    = self::get_filter_id( $slug ); // e.g. 'wp-duotone-filter-blue-orange'.                 $filter_value = self::get_css_var( $slug ); // e.g. 'var(--wp--preset--duotone--blue-orange)'.
                // CSS custom property, SVG filter, and block CSS.                 self::enqueue_global_styles_preset( $filter_id, $duotone_selector, $filter_value );

            }