How to convert JsonValue to String

[DenineLu]

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For DOM parser, how to convert JsonValue to byte array or string? For example:

byte[] json = toUtf8("{\"a\": {\"b\": \"c\"}}");
JsonValue jsonValue = parser.parse(json, json.length);
JsonValue res = jsonValue.get("a");

I want to get the string {"b": "c"}. Thank you in advance for your help with this question.