private SectionSelectionState getSectionSelectionState(int sectionIndex) {
        SectionSelectionState state = selectionStateBySection.get(sectionIndex);
        if (state != null) {
            return state;
        }

        state = new SectionSelectionState();
        selectionStateBySection.put(sectionIndex, state);

        return state;
    }
@param sectionIndex index of section
@return true if that section is collapsed
android/modules/module_common/src/main/java/github/tornaco/android/thanos/widget/section/SectioningAdapter.java