code: public CertificateEnvelope getWhitelistCertificate(String dtid) throws ApiException {
          ApiResponse<CertificateEnvelope> resp = getWhitelistCertificateWithHttpInfo(dtid);
          return resp.getData();
      }
docs: Get whitelist certificate of device type.
  Get whitelist certificate of device type.
  @param dtid Device Type ID. (required)
  @return CertificateEnvelope
  @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body