func apply(font: UIFont, subString: String)  {

        if let range = self.string.range(of: subString) {
            self.apply(font: font, onRange: NSRange(range, in: self.string))
        }
    }
    func apply(font: UIFont, onRange: NSRange) {
        self.addAttributes([NSAttributedString.Key.font: font], range: onRange)
    }