feature request: na_filter/na_values equivalent

[jsimon1080]

Hi,

I am using the calamine engine with the Polars python Library and I noticed that "None" values in my Excel files are being converted to null values. This is probably fine in general, but in my case I need to preserve "None" as a string value and actually only interpret empty cells as null values.

Is there any plan to add some options to control the interpretation of null values, for example "na_filter" and "na_values" as with pandas and openpyxl?

Thank you.

[tafia]

There is no such plan but I'd be happy to merge such PR if anyone wants it.