docs: def generate_url(query, num, start, recent, country_code):
      """(str, str, str) -> str
      A url in the required format is generated.
      """
      query = '+'.join(query.split())
      url = 'https://www.google.com/search?q=' + query + '&num=' + num + '&start=' + start
      if recent in ['h', 'd', 'w', 'm', 'y']:
          url += '&tbs=qdr:' + recent
      if country_code is not None:
          url += '&gl=' + country_code
      return url