public function delayedPayments()
{
$student = $this->with(['billets' => function ($b) {
$b->where('due_date', '<', date('Y-m-d'))->where('student_id', $this->id);
}])->whereHas('billets', function ($b) {
$b->where('due_date', '<', date('Y-m-d'))->where('student_id', $this->id);
})->first();
if (is_null($student)) {
return [];
}
return $student->billets;
}