code: public static String jsonToString(JsonNode node) {
          try {
              return node == null ? null : MAPPER.writeValueAsString(node);
          } catch (JsonProcessingException e) {
              throw new SdkClientException("Could not serialize JSON", e);
          }
      }
docs: Converts a {@link JsonNode} into a string.
  
  @param node Node to convert.
  @return String of JSON document.