Testing if belongsTo relationship has been

I have a ember-data model which has a belongsTo relationship and I'd like test whether there is any value (aka, foreign key reference) in this relationship. I initially thought I could just state:

if(myModel.rel !== null) {
    // do something now that belongsTo relationship has a value
}

But of course this doesn't work because myModel.rel would never be null and instead is some sort of Ember Data object. Ok fine. I adjusted this to:

if(myModel.rel.content !== null) {
    // do something now that belongsTo relationship has a value
}

This does work but I feel like maybe this is a bit too "hacky" ... is there a cleaner, more API driven way of stating this conditional in Ember Data?