Specify the missing value other than nan

[jnsofini]

I find now that with the binning_parameters I can specify a special code. I have a datast where missing are coded by a string "unknown" and "no value". I understand that I can replace these by nan in the preprocessiing stage. However, I am wondering if there is a way to specify the list of missing similar to special code. Something lime missing_codes = ["unknown", "no value", "_"]