         }
 
         let utf16 = self.utf16
-        guard let data = NSMutableData(capacity: utf16.count/2) else {
-            return nil
-        }
+        guard let data = NSMutableData(capacity: utf16.count/2) else { return nil }
 
         var i = utf16.startIndex
         while i != utf16.endIndex {

            data.append(&value, length: 1)
            i = index(i, offsetBy: 2, limitedBy: utf16.endIndex)!
        }
        return data
    }
}



//  https://codereview.stackexchange.com/questions/135424/hex-string-to-bytes-nsdata?newreg=06dfe1d5b9964b928631538c9e48d421
extension String {
    func dataFromHexString() -> Data? {

        // Convert 0 ... 9, a ... f, A ...F to their decimal value,
        // return nil for all other input characters
