It is not actually used anywhere (since the removal of the old pe), is very hard to read, and essentially contains a custom clone of std::tuple.
If it is ever needed, it could easily be re-implemented using std::tuple and variadic templates in significantly less code.

If you have access to the old closed source waLBerla repository, you may restore the complete history with the following command
git fetch git@i10git.cs.fau.de:software/walberla.git 'refs/replace/*:refs/replace/*'