docs: def rm_empty_doi(d):
      """
      If an "identifier" dictionary has no doi ID, then it has no use. Delete it.
  
      :param dict d: Metadata
      :return dict d: Metadata
      """
      logger_misc.info("enter remove_empty_doi")
      try:
          # Check each publication dictionary
          for pub in d['pub']:
              # If no identifier, then we can quit here. If identifier, then keep going.
              if 'identifier' in pub:
                  if 'id' in pub['identifier'][0]:
                      # If there's a DOI id, but it's EMPTY
                      if pub['identifier'][0]['id'] in EMPTY:
                          del pub['identifier']
                  else:
                      # If there's an identifier section, with no DOI id
                      del pub['identifier']
      except KeyError as e:
          # What else could go wrong?
          logger_misc.warn("remove_empty_doi: KeyError: publication key not found, {}".format(e))
      logger_misc.info("exit remove_empty_doi")
      return d