I made my approach ensure that only Operatives with Animal were replaced. I saw that some Null()'s came up when using a different method. My thought process was, assume operatives that were != "Animal" are already correct. I didn't want to make the assumption that the "Article" tag included the correct operative, or even the possibility of a different (or multiple) operative(s). I guess someone could make the argument that Operatives != "Animal" could also be potentially incorrect. Unclear data would obviously lead to questions to determine the actual correct approach.
But with a safe dataset like this, the above was probably over thinking the exercise 😉