Having a possibility to detect to which FoldOperation an instance of Fold belongs to, resp. which FoldManager created
the Fold would easy usecases when there are more FoldManager implementations bound to one mimetype.

Currently the problem can be partially solved by using Fold.getFoldType() which however returns an instance of final
class so no class instance resolution can be used. The problem gets worser in case of a generic FoldManager
implementation like Schlieman has which creates the FoldType-s based on some external metadata.

The only generic way I found is:

                        Fold f = fold.getFold (i);
                        try {
                            operation.getExtraInfo(f);
                            //no ISE thrown - my fold
                            l.add (f.getType());
                        } catch (IllegalStateException e) {
                            //not my fold
                        }

If for example getExtraInfo() is called on fold which wasn't created by this FoldManager, the ISE it thrown, so I know
that this is not my fold. This solution is IMHO no elegant enought, I would expect something like:

Fold.isCreatedBy(FoldOperation) or somethin similar.