code: public void setClientId(String clientId) throws HelloSignException {
          if (clientId == null) {
              throw new HelloSignException("Client ID cannot be null");
          }
          this.clientId = clientId.trim();
      }
docs: Associates this request with an API app.
  
  @param clientId String client ID of the API app.
  @throws HelloSignException thrown if clientId is null