function orReValues(ops){
    return ops
    .map(function(op) {
      return op
        .split('')
        .map(function(char) {
          return '\\' + char;
        })
        .join('');
    })
    .join('|');
  }
The `FUNCTION` and `CLASS` modes were intentionally removed to simplify
highlighting and fix cases like
```
interface Iterator[A: A]
  fun has_next(): Bool
  fun next(): A?
```
where it is valid to have a function head without a body