Hello! It isn’t quite evident for me in the task what the function should return: just a name of the best customer or the whole row in the list of lists!?
It should be the whole row. At the start of the screen we read:
In this problem, the input is,
list_of_customers— a list of lists where each of its elements represents the best customer of a given day in a popular online store.
So the customer is the whole row.