docs: public void marshall(CaptionSource captionSource, ProtocolMarshaller protocolMarshaller) {
  
          if (captionSource == null) {
              throw new SdkClientException("Invalid argument passed to marshall(...)");
          }
  
          try {
              protocolMarshaller.marshall(captionSource.getKey(), KEY_BINDING);
              protocolMarshaller.marshall(captionSource.getLanguage(), LANGUAGE_BINDING);
              protocolMarshaller.marshall(captionSource.getTimeOffset(), TIMEOFFSET_BINDING);
              protocolMarshaller.marshall(captionSource.getLabel(), LABEL_BINDING);
              protocolMarshaller.marshall(captionSource.getEncryption(), ENCRYPTION_BINDING);
          } catch (Exception e) {
              throw new SdkClientException("Unable to marshall request to JSON: " + e.getMessage(), e);
          }
      }