private static <T> T parseJsonString(String content, TypeReference<T> typeReference)
            throws JsonProcessingException {
        return mapper.readValue(content, typeReference);
    }
This only works reliably if maybeMap is from Json, as maps(objects) in Json
can only have string keys.
graphql-protocol/src/main/java/com/linecorp/armeria/server/graphql/protocol/AbstractGraphqlService.java