Unknown switch or valve

I cannot take ignition key out even though shifter is in Park , tumbler will not go to the position where the key can be taken out . Took covers off steering and there is a white colored switch or vacuum valve with a button that goes in and out depending on the position of the shifter . What is the function of that whatever it is called . showed car to dealers parts dept. and they could not tell me or find that part in the schematics . Could that part has gone bad or there is a different reason why the key will not come out when in Park .