Check if file exists on the SD card in UIFlow

[csongor.varga]

Does anyone have an example how to check if a file exists of an SD card?
I tried isFile but the code just stops, nothing happens. listdir does not appear to return anything useful.
I am using a UIFlow desktop app 1.9.5, M5Go which has 1.8.1 firmware on it.
Creating a new file on the sdcard and writing to that file works.

[csongor.varga]

I have upgraded my M5Go to 1.11.0, but there is still no change. There is no documentation on these sdcard functions at all: is this is the entire documentation? http://docs.m5stack.com/en/uiflow/advanced/sdcard
This is rubbish.