presto-main/src/main/java/io/prestosql/operator/scalar/JsonExtract.java/JsonExtract/processJsonObject
class JsonExtract:        public T processJsonObject(JsonParser jsonParser)
                throws IOException
        {
            while (!jsonParser.nextFieldName(fieldName)) {
                if (!jsonParser.hasCurrentToken()) {
                    throw new JsonParseException(jsonParser, "Unexpected end of object");
                }
                if (jsonParser.getCurrentToken() == END_OBJECT) {
                    // Unable to find matching field
                    return null;
                }
                jsonParser.skipChildren(); // Skip nested structure if currently at the start of one
            }

            jsonParser.nextToken(); // Shift to first token of the value

            return delegate.extract(jsonParser);
        }