1. remove comment
2. cannot refer to "self.property" in `dealloc`

From [Advanced Memory Management Programming Guide]()
> **Don’t Use Accessor Methods in Initializer Methods and dealloc**
> The only places you shouldn’t use accessor methods to set an instance variable are in initializer methods and dealloc.

Because of (2) this should remain `_keyboardView = nil;` and observers should be removed manually.