[TYPO3] delete session - unset session

[Anders Tillbeck]

Hi

I am working with a session variable in an extension. I can set the 
session and get the session but how do I delete the session?

Set $value:
$GLOBALS["TSFE"]->fe_user->setKey("ses", "bb_fe_user", $value);

Get $value:
$GLOBALS['TSFE']->fe_user->getKey('ses','bb_fe_user');

delete session:
??

I have tried many things but get some random errors that may be due to 
my test server setup.

BR. Anders