code: def _init_hdrgo2sections(self):
          
          hdrgo2sections = cx.defaultdict(list)
          for section_name, hdrgos in self.sections:
              for hdrgo in hdrgos:
                  hdrgo2sections[hdrgo].append(section_name)
          return hdrgo2sections
docs: Return a dict with GO group headers as keys and section(s) as values.