loadFilePromise() method unavailable in the Loader class using FB 4.7 (target iOS)

Here's my code:

Note that mpLoader is declared as a Loader class, yet when I try to use the loadFilePromise() method, it won't accept it syntactically.

Is there a reason for this?  I've checked and triple checked in the online docs ... It just shows me examples where  loadFilePromise() obviously works ...

What's wrong with this code? Why won't it work?