code: def make_cookie_header
        return nil if cookie_jar.nil?
  
        arr = cookie_jar.cookies(url)
        return nil if arr.empty?
  
        return HTTP::Cookie.cookie_value(arr)
      end
docs: Render a Cookie HTTP request header from the contents of the @cookie_jar,
   or nil if the jar is empty.
  
   @see Request#cookie_jar
  
   @return [String, nil]