I know what I'm looking for. I want python to tell me which list it's in.

Here's some pseudocode:

item = "a"

nested_list = [["a", "b"], ["c", "d"]]

list.index(item) #obviously this doesn't work

here I would want python to return 0 (because "a" is an element in the first sub-list in the bigger list). I don't care which sub-element it is. I don't care if there are duplicates, e.g., ["a", "b", "a"] should return the same thing as the above example.

Sorry if this is a dumb question. I'm new to programming.