Option groups for select don't work

[wvdongen]

Option groups for select elements do not work

{!! Form::select('cars', 'Choose your Car')->options([
    'Swedish Cars' => [1 => 'Volvo', 2 => 'Saab'],
    'German Cars' => [1 => 'Mercedes', 2 => 'Audi']
]) !!}

This results in Array to string conversion