code: public ApiSuccessResponse sendDTMF(String id, SendDTMFData sendDTMFData) throws ApiException {
          ApiResponse<ApiSuccessResponse> resp = sendDTMFWithHttpInfo(id, sendDTMFData);
          return resp.getData();
      }
docs: Send digits as DTMF
  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 id The connection ID of the call. (required)
  @param sendDTMFData  (required)
  @return ApiSuccessResponse
  @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body