code: public boolean isValidSecretToken(String secretToken) {
          return (this.secretToken == null || this.secretToken.equals(secretToken) ? true : false);
      }
docs: Validate the provided secret token against the reference secret token. Returns true if
  the secret token is valid or there is no reference secret token to validate against,
  otherwise returns false.
  
  @param secretToken the token to validate
  @return true if the secret token is valid or there is no reference secret token to validate against