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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_cancelpayment( payment_state: InitiatorPaymentState, channelidentifiers_to_channels: ChannelMap, ) -> TransitionResult[InitiatorPaymentState]: """ Cancel the payment and all related transfers. """

    # Cannot cancel a transfer after the secret is revealed
    events = list()
    for initiator_state in payment_state.initiator_transfers.values():
        channel_identifier = initiator_state.channel_identifier
        channel_state = channelidentifiers_to_channels.get(channel_identifier)

        if not channel_state:
            continue

        if can_cancel(initiator_state):
            transfer_description = initiator_state.transfer_description
            cancel_events = cancel_current_route(payment_state, initiator_state)

            initiator_state.transfer_state = 'transfer_cancelled'

            cancel = EventPaymentSentFailed(
                payment_network_identifier=channel_state.payment_network_identifier,
                token_network_identifier=TokenNetworkID(channel_state.token_network_identifier),
                identifier=transfer_description.payment_identifier,
                target=transfer_description.target,
                reason='user canceled payment',
            )
            cancel_events.append(cancel)

            events.extend(cancel_events)

    return TransitionResult(payment_state, events)