Examine the code in the code editor. Four different functions are defined: sum$\_$list$1,$ sum$\_$list$2,$ sum$\_$list$3,$ and sum$\_$list$4.$ Except for being indented differently, they all contain the same sequence of code operations. What these functions are trying to do is add up all the elements in a list, by first initializing a running total, then adding each element of that list to the total, and then returning the total at the end. But only one of these functions actually works as intended. Recall that in a for loop over a list, a variable is assigned to each element of the list in turn, and that variable has the value of the last element of the list once the for loop is exited. Recall also that a function returns a value as soon as the first return statement is encountered, even if that statement is not the last one in the function definition.

Run exercise.py in the interpreter. You should notice that an IndentationError is reported.