usage:
- build shared lib:
go build -buildmode=c-shared -o library.so main.go
- use it
python3 metricsql.py 'not_exist(up)'`
failed to parse expr: not_exist(up), error: unsupported function "not_exist"
python3 metricsql.py 'rate(up) > 1'
expr: rate(up) > 1 is valid
NOTE result of parseExpr doesn't free memory, so it's recommened to use only for ad-hoc valition.