Flatten([1,["a","b",[2,3,4],"c","d"],5,6]);
[1, "a", "b", 2, 3, 4, "c", "d", 5, 6]
-------------------------------
L := [1,2, [3,4], [5, [6,7,[8,9]]]];
Flatten(L,1);
[1, 2, 3, 4, 5, [6, 7, [8, 9]]]
-------------------------------
Flatten(It,1);
[1, 2, 3, 4, 5, 6, 7, [8, 9]]
-------------------------------
Flatten(L,2); -- same as in the previous line
[1, 2, 3, 4, 5, 6, 7, [8, 9]]
-------------------------------
Flatten(L,3); -- same as Flatten(L)
[1, 2, 3, 4, 5, 6, 7, 8, 9]
-------------------------------
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