First, I want to know how Python's list.extend method works under the hood, because I did not specify that I was using Python in my question.

Second, I have a subtle question about terminology here. Does `dosomething(x)` *return* a list, or *is* it a list? It seems to me like the function `dosomething` should return a list while the evaluation of the function `dosomething(x)` should actually *be* a list. I may be wrong in the domain of programming parlance though, please educate me!
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