Car keys

Hello!!
I recently did kunskapsprov and one of the question was is it punishable by law to leave your car keys in the car which is parked in a parking lot.
Does anyone know what’s the answer to this question?

Yes, it is forbidden. It does not say explicitly in the law, but this is to be interpreted as a prohibition to leave the keys in the car:

”When a vehicle is stopped or parked, the driver shall take measures to prevent the vehicle from moving on its own.
The driver of a motor vehicle shall also take appropriate measures to prevent the vehicle from being used by someone else without authorisation.” (Road Traffic Ordinance, Google Translate)