docs: def generate_url(query, first, recent, country_code):
      """(str, str) -> str
      A url in the required format is generated.
      """
      query = '+'.join(query.split())
      url = 'http://www.bing.com/search?q=' + query + '&first=' + first
      if recent in ['h', 'd', 'w', 'm', 'y']: # A True/False would be enough. This is just to maintain consistancy with google.
          url = url + '&filters=ex1%3a%22ez1%22'
      if country_code is not None:
          url += '&cc=' + country_code
      return url