Implementation for being able to extract the key from an object if only
a single argument is passed.
@private
@param {String} key The key
@param {Object} value The value
@return {Array} [key, value]
function(key, value) {
        // if we have no value, it means we need to get the key from the object
        if (value === undefined) {
            value = key;
            key = this.getKey(value);
        }

        return [key, value];
    }