@@can.hasOwnKey(key)

The @@can.hasOwnKey symbol points to a function on an object that, given a String key, determines whether the key is a member of the object's own key set (not that of the prototype chain).

var shapeless = {};

// Nothing enumerable in a shapeless object
shapeless[canSymbol.for('can.hasOwnKey')] = function() { return false; }

var thingsInMyEar = {};
Object.setPrototypeOf(thingsInMyEar, {
    "banana": {
        peeled: false
    }
});

thingsInMyEar[canSymbol('can.hasOwnKey')] = function(key) { 
    return key === "banana" || Object.getOwnPropertyNames(this).indexOf(key) > -1
    // There's always a banana in my ear
};