firefly-iii/app/Models/PeriodStatistic.php

<?php

declare(strict_types=1);

namespace FireflyIII\Models;

use Carbon\Carbon;
use FireflyIII\Casts\SeparateTimezoneCaster;
use FireflyIII\Support\Models\ReturnsIntegerUserIdTrait;
use Illuminate\Database\Eloquent\Casts\Attribute;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use Illuminate\Database\Eloquent\Relations\MorphTo;

/**
 * @property Carbon $start
 * @property Carbon $end
 * @property string $amount
 */
class PeriodStatistic extends Model
{
    use ReturnsIntegerUserIdTrait;

    public function primaryStatable(): MorphTo
    {
        return $this->morphTo();
    }

    public function secondaryStatable(): MorphTo
    {
        return $this->morphTo();
    }

    public function tertiaryStatable(): MorphTo
    {
        return $this->morphTo();
    }

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

    protected function casts(): array
    {
        return [
            'created_at' => 'datetime',
            'updated_at' => 'datetime',
            'start'      => SeparateTimezoneCaster::class,
            'end'        => SeparateTimezoneCaster::class,
        ];
    }

    protected function count(): Attribute
    {
        return Attribute::make(get: static fn ($value): int => (int) $value);
    }
}