Swift playgrounds ios 10 text to speech command code

I'm using swift playgrounds on iOS iPad to create a text to speech command. Below is the code.

import AVFoundation
let synthesizer = AVSpeechSynthesizer()
let utterance = AVSpeechUtterance (string: "Say     
Hello")
utterance.rate = 1
synthesizer.speak(utterance:   
AVSpeechUtterance)

//when I hit "run my code". I get the error message "Attempt to evaluate editor placeholder" I don't know what this error means. Hopefully someone can help. Thank you.