Is there BUG?

I solved it & all test are passed. But I have the message ""The Flat Dictionary" mission doesn't accept solutions" It's not clear WHY? & who can explain why Also I can't see the solutions from another guys.

Thanks in advance, Alexey

P.S. My solution: def flatten(dictionary): stack = [((), dictionary)] result = {} while stack: path, current = stack.pop() if not current: result["/".join(path)] = '' for k, v in current.items(): if isinstance(v, dict): stack.append((path + (k,), v)) else: result["/".join((path + (k,)))] = v return result

From: https://py.checkio.org/mission/flatten-dict/solve/

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