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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 clear_if_finalized( iteration: TransitionResult, ) -> TransitionResult[InitiatorPaymentState]: """ Clear the initiator payment task if all transfers have been finalized or expired. """

    state = cast(InitiatorPaymentState, iteration.new_state)

    if state is None:
        return iteration

    if len(state.initiator_transfers) == 0:
        return TransitionResult(None, iteration.events)

    return iteration