code: def find_country(session, code):
      
      country = session.query(Country).\
          filter(Country.code == code).first()
  
      return country
docs: Find a country.
  
      Find a country by its ISO-3166 `code` (i.e ES for Spain,
      US for United States of America) using the given `session.
      When the country does not exist the function will return
      `None`.
  
      :param session: database session
      :param code: ISO-3166 code of the country to find
  
      :return: a country object; `None` when the country
          does not exist