docs: def _merge_tops_merge(self, tops):
          '''
          The default merging strategy. The base env is authoritative, so it is
          checked first, followed by the remaining environments. In top files
          from environments other than "base", only the section matching the
          environment from the top file will be considered, and it too will be
          ignored if that environment was defined in the "base" top file.
          '''
          top = DefaultOrderedDict(OrderedDict)
  
          # Check base env first as it is authoritative
          base_tops = tops.pop('base', DefaultOrderedDict(OrderedDict))
          for ctop in base_tops:
              for saltenv, targets in six.iteritems(ctop):
                  if saltenv == 'include':
                      continue
                  try:
                      for tgt in targets:
                          top[saltenv][tgt] = ctop[saltenv][tgt]
                  except TypeError:
                      raise SaltRenderError('Unable to render top file. No targets found.')
  
          for cenv, ctops in six.iteritems(tops):
              for ctop in ctops:
                  for saltenv, targets in six.iteritems(ctop):
                      if saltenv == 'include':
                          continue
                      elif saltenv != cenv:
                          log.debug(
                              'Section for saltenv \'%s\' in the \'%s\' '
                              'saltenv\'s top file will be ignored, as the '
                              'top_file_merging_strategy is set to \'merge\' '
                              'and the saltenvs do not match',
                              saltenv, cenv
                          )
                          continue
                      elif saltenv in top:
                          log.debug(
                              'Section for saltenv \'%s\' in the \'%s\' '
                              'saltenv\'s top file will be ignored, as this '
                              'saltenv was already defined in the \'base\' top '
                              'file', saltenv, cenv
                          )
                          continue
                      try:
                          for tgt in targets:
                              top[saltenv][tgt] = ctop[saltenv][tgt]
                      except TypeError:
                          raise SaltRenderError('Unable to render top file. No targets found.')
          return top