"Cannot find module 'horizon/ui' or its corresponding type declarations."

I've copied the script from this tutorial page

Meta Developers

the second line has this code block

import * as hz from 'horizon/core';

import { UIComponent, View, Text, Binding, } from "horizon/ui";

When i put it in my script i get this error: 
Cannot find module 'horizon/ui' or its corresponding type declarations.

What is happening here?