public HeaderPositionChangedCallback getHeaderPositionChangedCallback() {
        return headerPositionChangedCallback;
    }
Called when a sections header positioning approach changes. The position can be HeaderPosition.NONE, HeaderPosition.NATURAL, HeaderPosition.STICKY or HeaderPosition.TRAILING

@param sectionIndex the sections [0...n)
@param header       the header view
@param oldPosition  the previous positioning of the header (NONE, NATURAL, STICKY or TRAILING)
@param newPosition  the new positioning of the header (NATURAL, STICKY or TRAILING)
android/modules/module_common/src/main/java/github/tornaco/android/thanos/widget/section/StickyHeaderLayoutManager.java