code: def add_checkin_reply(checkin_id, options={})
        response = connection.post do |req|
          req.url "checkins/#{checkin_id}/reply", options
        end
        return_error_or_body(response, response.body.response.reply)  
      end
docs: Add a reply to a checkin.
  
   @param [String] checkin_id the ID of the checkin.
   @param [Hash]  options
   @option options String :text - The text of the post, up to 200 characters.
   @option options String :url - Link for more details. This page will be opened in an embedded web view in the foursquare application, unless contentId is specified and a native link handler is registered and present. We support the following URL schemes: http, https, foursquare, mailto, tel, and sms.
   @option options String :contentId - Identifier for the post to be used in a native link, up to 50 characters. A url must also be specified in the request.