def rucaptcha_sesion_key_key
      session_id = session.respond_to?(:id) ? session.id : session[:session_id]
      warning_when_session_invalid if session_id.blank?
      ['rucaptcha-session', session_id].join(':')
    end
def rucaptcha_sesion_key_key
      session_id = session.respond_to?(:id) ? session.id : session[:session_id]
      warning_when_session_invalid if session_id.blank?
      ['rucaptcha-session', session_id].join(':')
    end
session key of rucaptcha