docs: public void marshall(Captions captions, ProtocolMarshaller protocolMarshaller) {
  
          if (captions == null) {
              throw new SdkClientException("Invalid argument passed to marshall(...)");
          }
  
          try {
              protocolMarshaller.marshall(captions.getMergePolicy(), MERGEPOLICY_BINDING);
              protocolMarshaller.marshall(captions.getCaptionSources(), CAPTIONSOURCES_BINDING);
              protocolMarshaller.marshall(captions.getCaptionFormats(), CAPTIONFORMATS_BINDING);
          } catch (Exception e) {
              throw new SdkClientException("Unable to marshall request to JSON: " + e.getMessage(), e);
          }
      }