cssd-back/app/Models/Option.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use Illuminate\Database\Eloquent\Relations\HasOne;

class Option extends Model
{
    public $fillable = ['title', 'input_id'];

    public function input(): BelongsTo
    {
        return $this->belongsTo(Input::class);
    }

    public function input_value(): HasOne
    {
        return $this->hasOne(InputValue::class);
    }
}