This function will also set "Cache-Control: no-cache="set-cookie"" header to inform caches that the cookie value should not be cached.
Here is one way to use this function:
c = Cookie.Cookie('spam', 'eggs', expires=time.time()+300)
Cookie.add_cookie(req, c)
Cookie.add_cookie(req, 'spam', 'eggs', expires=time.time()+300)
Cookie. Data
  can be any number of keyword arguments which, will be passed to
  parse() (This is useful for signedCookie and
  MarshalCookie which require secret as an additional
  argument to parse).