I have the following code:

```
enum Foo {
  a,
  b,
  c
}

type Bar = {
  [key in keyof typeof Foo]: string;
}

const test: Bar = {
  a: 'a',
  b: 'b'
};

```

The code complains that the `test` variable does not have the `c` property.

How can I alter the `Bar` type so that the keys from the enum are optional?