mlr3 - dalex パッケージについて少し混乱

Question

こんにちは、mlr3 チームです。

mlr3 本で提供されている dalex パッケージについて質問があります。具体的にはこちら

ranger_exp <- explain_mlr3(fifa_ranger,
        data     = fifa,
        y        = fifa$value_eur,
        label    = "Ranger RF",
        colorize = FALSE)

(a) 'fifa' here is a training data or full data which also include test sets?

(b) I read somewhere that it should not include the class variable but here it appears to include? 

(c) For the instance level explanation, like fifa["Cristiano Ronaldo",], which feature/column of the observation/row need to be included here, if we do not have a unique column (like iD or name) in our dataset? 

前もって感謝します