neptunesoftware / laravel-invoice

src/Traits/HasInvoice.php

<?php

namespace NeptuneSoftware\Invoice\Traits;

use NeptuneSoftware\Invoice\Models\Bill;
use NeptuneSoftware\Invoice\Models\Invoice;
use NeptuneSoftware\Invoice\Models\InvoiceLine;

trait HasInvoice
{
    /**
     * Set the polymorphic relation.
     *
     * @return mixed
     */
    public function invoices()
    {
        return $this->morphMany(Invoice::class, 'related');

It seems like morphMany() must be provided by classes using this trait. How about adding it as abstract method to this trait?

    }

    /**
     * @return mixed
     */
    public function bills()
    {
        return $this->morphMany(Bill::class, 'related');
    }
}