Introducing calling with multiple arguments

[alexmojaki]

In the course I try hard to introduce one concept at a time, so that the user learns gradually. Currently this is violated in an exercise under the page "Functions And Methods For Lists" where the user has to do some googling and submit the code nums.insert(2, 9). They've seen function and method calls a few times by now, but critically they've never seen multiple arguments separated by commas before. At some point before this exercise, this syntax needs to be shown to them.