public void addSection(final int index, final String tag, final Section section) {
        this.sections.put(index, tag, section);
        addSectionViewTypeNumbers(tag);

        final SectionAdapter result = sectionAdapters.put(section, new SectionAdapter(this, section));
        if (result != null) {
            throw new IllegalArgumentException("This adapter already contains this Section");
        }
    }
Add a section to this adapter at the specific index.

@param index   the index at which the section should be inserted
@param tag     unique identifier of the section
@param section section should be added
library/src/main/java/io/github/luizgrp/sectionedrecyclerviewadapter/SectionedRecyclerViewAdapter.java