code: def add_nations_field(authors_subfields):
      
      from .config import NATIONS_DEFAULT_MAP
      result = []
      for field in authors_subfields:
          if field[0] == 'v':
              values = [x.replace('.', '') for x in field[1].split(', ')]
              possible_affs = filter(lambda x: x is not None,
                                     map(NATIONS_DEFAULT_MAP.get, values))
              if 'CERN' in possible_affs and 'Switzerland' in possible_affs:
                  # Don't use remove in case of multiple Switzerlands
                  possible_affs = [x for x in possible_affs
                                   if x != 'Switzerland']
  
              result.extend(possible_affs)
  
      result = sorted(list(set(result)))
  
      if result:
          authors_subfields.extend([('w', res) for res in result])
      else:
          authors_subfields.append(('w', 'HUMAN CHECK'))
docs: Add correct nations field according to mapping in NATIONS_DEFAULT_MAP.