Please also add a note where the iterator will point if number is unspecified. Not immediately obvious to me. I would have thought it simply defaults to "0", but that seems not true.
Still puzzled where the difference between ```setUnfilteredPosition(node, 0)``` and ```setUnfilteredPosition(node)``` is and should be. I assume in the latter case the first parameter ```container``` no longer is the container, but instead the node itself in front of which the iterator should be set, right?

These two variants how to use the call then need to be made more obvious in the API dox. By clearly stating there are two different ways how to call that. And perhaps by renaming the first parameter, perhaps to "node".