Typo3 How to render RTE content of an extension

When writing your own Typo3 extension you may come to the day where you need to enter some free HTML content. This content may also include some links. No Problem so far. But if you save the stuff to the db Typo3 transforms the text. For example all a-Tags are written as <link XX>Test</link> and so on.
So when you like to render the text you need to revert the transformation. (At this point it doesn’t matter if you are using FlexForms or the traditional TCA configuration).
All you need to do is to call this method and everything goes fine:
[sourcecode lang=“php“]$outputText=$this->pi_RTEcssText($dbtext);[/sourcecode]