code: public void sendDTMF(String connId, String digits) throws WorkspaceApiException {
          this.sendDTMF(connId, digits, null, null);
      }
docs: Send DTMF digits to the specified call. You can send DTMF digits individually with multiple requests or together with multiple digits in one request.
  @param connId The connection ID of the call.
  @param digits The DTMF digits to send to the call.