code: public static ExternalSessionKey fromResponseBody(String responseBody) throws NewSessionException {
      if (responseBody != null && responseBody.startsWith("OK,")) {
        return new ExternalSessionKey(responseBody.replace("OK,", ""));
      }
      throw new NewSessionException("The server returned an error : "+responseBody);
    }
docs: extract the external key from the server response for a selenium1 new session request.
  @param responseBody the response from the server
  @return the ExternalKey if it was present in the server's response.
  @throws NewSessionException in case the server didn't send back a success result.