[gentoo-user] How to acchieve the opposite of 'provided'...so to say ?

Hi,

I want to make certain packages immune against "emerge --depclean"
even when startet without "--pretend" (or other actions to remove
packages which emerge evaluates as obsoloted and no longe in use).

How can I acchieve this?

Thank you very much for any help in advance!
Have a nce sunday!
Best regards,
mcc