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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 handle_offchain_secretreveal( target_state: TargetTransferState, state_change: ReceiveSecretReveal, channel_state: NettingChannelState, pseudo_random_generator: random.Random, block_number: BlockNumber, ) -> TransitionResult[TargetTransferState]: """ Validates and handles a ReceiveSecretReveal state change. """

    valid_secret = is_valid_secret_reveal(
        state_change=state_change,
        transfer_secrethash=target_state.transfer.lock.secrethash,
        secret=state_change.secret,
    )
    has_transfer_expired = channel.is_transfer_expired(
        transfer=target_state.transfer,
        affected_channel=channel_state,
        block_number=block_number,
    )

    if valid_secret and not has_transfer_expired:
        channel.register_offchain_secret(
            channel_state=channel_state,
            secret=state_change.secret,
            secrethash=state_change.secrethash,
        )

        route = target_state.route
        message_identifier = message_identifier_from_prng(pseudo_random_generator)
        target_state.state = TargetTransferState.OFFCHAIN_SECRET_REVEAL
        target_state.secret = state_change.secret
        recipient = route.node_address

        reveal = SendSecretReveal(
            recipient=recipient,
            channel_identifier=CHANNEL_IDENTIFIER_GLOBAL_QUEUE,
            message_identifier=message_identifier,
            secret=target_state.secret,
        )

        iteration = TransitionResult(target_state, [reveal])

    else:
        # TODO: event for byzantine behavior
        iteration = TransitionResult(target_state, list())

    return iteration