code: public static Event constructEvent(String payload, String sigHeader, String secret)
        throws SignatureVerificationException {
      return constructEvent(payload, sigHeader, secret, DEFAULT_TOLERANCE);
    }
docs: Returns an Event instance using the provided JSON payload. Throws a
  JsonSyntaxException if the payload is not valid JSON, and a
  SignatureVerificationException if the signature verification fails for
  any reason.
  
  @param payload   the payload sent by Stripe.
  @param sigHeader the contents of the signature header sent by Stripe.
  @param secret    secret used to generate the signature.
  @return the Event instance
  @throws SignatureVerificationException if the verification fails.