private function requisites($type_id)
{
$instance = new Course();
$relation = $this->getBelongsToManyCaller();
$foreignKey = 'course_id';
$otherKey = 'course_requisite_id';
$table = 'requisites';
$query = $instance->newQuery()->where('requisite_type_id', $type_id);
return new BelongsToMany($query, $this, $table, $foreignKey, $otherKey, $relation);
}
