20Flatten a Nested List
Mediumrecursionlists
Write flatten(items) that takes a list which may contain other lists (nested to any depth) and returns a single flat list of all the non-list values, in order.
Examples
Example 1
>>> flatten([1, [2, 3], [4, [5, 6]]]) [1, 2, 3, 4, 5, 6]
Example 2
>>> flatten([[['deep']]]) ['deep']
Run examples checks the 2 examples above. Submit runs all 6 tests, including hidden edge cases, and marks the challenge solved.