if chapters[chapter_l1][chapter_l2].get(nic, None) is None:
chapters[chapter_l1][chapter_l2][nic] = dict(
rst_file=f"{join(table_set, chapter_l1)}_{nic}.rst".
if chapters[chapter_l1][chapter_l2].get(nic, None) is None:
chapters[chapter_l1][chapter_l2][nic] = dict(
rst_file=f"{join(table_set, chapter_l1)}_{nic}.rst".