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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def key_swap( d, cls, marshal ):
 """ Swap the keys in a dictionary Args: d: dict, The dict to swap keys in cls: class, If the class has a staticly defined _marshal_key_swap and/or _unmarshal_key_swap dict, the keys will be swapped. Otherwise @d is returned marshal: bool, True if marshalling class to JSON, False if unmarshalling JSON to class Returns: dict """

    dname = '_{}marshal_key_swap'.format("" if marshal else "un")
    if hasattr(cls, dname):
        key_swap = getattr(cls, dname)
        return {
            key_swap[k] if k in key_swap else k: v
            for k, v in d.items()
        }
    else:
        return d