public function addConstraints()
{
if (static::$constraints) {
// For belongs to relationships, which are essentially the inverse of has one
// or has many relationships, we need to actually query on the primary key
// of the related models matching on the foreign key that's on a parent.
$table = $this->related->getTable();
$this->query->where($table . '.' . $this->otherKey, '=', $this->parent->{$this->foreignKey});
}
}