public int getAdapterPositionForSectionFooter(int sectionIndex) {
        if (doesSectionHaveFooter(sectionIndex)) {
            Section section = this.sections.get(sectionIndex);
            int adapterPosition = section.adapterPosition;
            return adapterPosition + section.length - 1;
        } else {
            return NO_POSITION;
        }
    }
Return the adapter position corresponding to the footer of the provided section

@param sectionIndex the index of the section
@return adapter position of that section's footer, or NO_POSITION if section does not have footer
android/modules/module_common/src/main/java/github/tornaco/android/thanos/widget/section/SectioningAdapter.java