code: public SignatureRequest requestEmailReminder(String requestId, String email) throws HelloSignException {
          String url = BASE_URI + SIGNATURE_REQUEST_REMIND_URI + "/" + requestId;
          return new SignatureRequest(
                  httpClient.withAuth(auth).withPostField(Account.ACCOUNT_EMAIL_ADDRESS, email).post(url).asJson());
      }
docs: Instructs HelloSign to email the given address with a reminder to sign
  the SignatureRequest referenced by the given request ID.
  
  Note: You cannot send a reminder within 1 hours of the last reminder that
  was sent, manually or automatically.
  
  @param requestId String SignatureRequest ID
  @param email String email
  @return SignatureRequest The request to be reminded
  @throws HelloSignException thrown if there's a problem processing the
  HTTP request or the JSON response.