converting HTML to NSAttributedString "pseudo-asynchronously"

HTML_to_NSAttributedString.swift

import UIKit

extension NSAttributedString {
    static func fromHTML(_ html: String, execute: @escaping (NSAttributedString?) -> Void) {
        DispatchQueue.main.async {
            let options = [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.html]
            
            // only run on main queue
            let result = try? NSAttributedString(data: Data(html.utf8), options: options, documentAttributes: nil)
            
            execute(result)
        }
    }
}

NSAttributedString.fromHTML("hello <u>world</u>") { attrStr in
    // attrStr is an NSAttributedString?
}