Laravel Route - Where is prefix method

In my example, I have define router like

Route::prefix('home')->group(function(){
    Route::get('/test',....);
});

And i access mydomain/home/test. That is working but i don't know where is prefix method?. I think it in Illuminate\Routing\Route.php. But when i remove prefix method on that, it still working?

via Chebli Mohamed