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);
        }
    }
Converts a {@link JsonNode} into a string.

@param node Node to convert.
@return String of JSON document.
aws-java-sdk-stepfunctions/src/main/java/com/amazonaws/services/stepfunctions/builder/internal/JacksonUtils.java