public function belongsToOne($model, $thisKey = null, $parentKey = null)
	{
		$parent = $this->resolve($model);

		// Default the keys if not set
		$thisKey   = $thisKey   ?: strtolower($parent->getModelName()) . '_id';
		$parentKey = $parentKey ?: $this->getPrimaryKey();

		return new BelongsToOne($this, $parent, $thisKey, $parentKey);
	}