code: def get_fields(desc2nts):
          
          if 'flat' in desc2nts:
              nts_flat = desc2nts.get('flat')
              if nts_flat:
                  return nts_flat[0]._fields
          if 'sections' in desc2nts:
              nts_sections = desc2nts.get('sections')
              if nts_sections:
                  return nts_sections[0][1][0]._fields
docs: Return grouped, sorted namedtuples in either format: flat, sections.