python

We say that a list that contains lists is nested. The result of unnesting (also known as flattening) a nested list is a list that contains the same non-list elements as the nested list, in the same order, but in a single list.

For example, [1, [2], [[3], [[4], 5]]] is a nested list. The unnesting of this list is [1, 2, 3, 4, 5].

Write a function called unnest that takes as argument a list, which may be nested, and returns the unnesting of the argument list.

You should assume that the argument is a list, and that all elements in the list are either lists or some non-sequence type.

Your function must not modify the argument list. It must return a value of type list.