Some examples of possible inputs and corresponding return values: flatten ([[1,2,3], [4,5,6], [7,8,9] 1) should evaluate to 11. 2. B 4, 5, 6, 7, 8, 9] flatten ([[1,2,3], [4, 5], [6], [], [100,101] 1) should evaluate to [1, 2, 3, 4, 5, 6, 100, 101] flatten ([]) should evaluate to [] flatten ([[1, 'a'], ['hi', [100, 200]], [2.8,['one :1),None], [[1.-5] should evaluate to [1, 'a', 'hi, [100, 200], 2.0, ('one':1), None, [], -5] (i.e., you do not need to know, or care, what the types of the nested elements are.. do not over-complicate). Write a function flatten() which takes a list of lists ns as an argument and returns a new list, which contains all the nested elements directly (see examples). The input argument(s) should not be modified in any way. . Just to make this absolutely clear, the "flattening" is "single-level" only (as also illustrated by the last example). I.e., if one of the nested elements is a list (e.g., [100,200] or [] in the above example), that doesn't matter (it stays a list-or whatever it was). Implementing a "flatten all the way down" operation would require recursion, which is beyond the scope of this class. Hint: Note that, for instance, in the second example above, the result [1, 2, 3, 4, 5, 6, 100, 101] is simply [1,2,3] + [4, 5] + [6] + []+[100, 101]. That should tell you what kind of accumulation this is (it should be a very familiar one, even syntactically)...