When pushed, it seems they are relying on dict.get returning None if the key is not in the dict, but fail to see tha if the key being tested is in the dict, but has a value of None then their test fails.
# But adding a key of x with value None gives # The correct way is to use 'in' "Pythonic IMPLEMENTATION" # And now for keys with None as a value: Ugly, code-golf solution using Ugly, code-golf solution using dict.get()
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