docs: def get_client_token():
      """
      Requests and stores the NOMIS API client token from mtp-api
      """
      if getattr(settings, 'NOMIS_API_CLIENT_TOKEN', ''):
          return settings.NOMIS_API_CLIENT_TOKEN
      global client_token
      if not client_token or client_token['expires'] and client_token['expires'] - now() < datetime.timedelta(days=1):
          session = None
          try:
              session = api_client.get_authenticated_api_session(settings.TOKEN_RETRIEVAL_USERNAME,
                                                                 settings.TOKEN_RETRIEVAL_PASSWORD)
              client_token = session.get('/tokens/nomis/').json()
          except (requests.RequestException, HttpNotFoundError, ValueError, AttributeError):
              logger.exception('Cannot load NOMIS API client token')
              return None
          finally:
              if session and getattr(session, 'access_token', None):
                  api_client.revoke_token(session.access_token)
          if client_token.get('expires'):
              client_token['expires'] = parse_datetime(client_token['expires'])
              if client_token['expires'] < now():
                  logger.error('NOMIS API client token from mtp-api had expired')
                  return None
      return client_token['token']