what the heck is this |. operator?  I haven't seen it in the Reason language basics

Sorry to bother, I just had to ask.  Obviously I'm just a curious observer of Reason rather than a user.

E.g.
```
document |. getBody |. appendChild1(app |. getView);
```

From the Reason language basics docs I would think it would simply be
```
document.getBody.appendChild1(app.getView);
```