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
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
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]