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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 next_channel_from_routes( available_routes: List[RouteState], channelidentifiers_to_channels: ChannelMap, transfer_amount: PaymentAmount, ) -> Optional[NettingChannelState]: """ Returns the first channel that can be used to start the transfer. The routing service can race with local changes, so the recommended routes must be validated. """

    for route in available_routes:
        channel_identifier = route.channel_identifier
        channel_state = channelidentifiers_to_channels.get(channel_identifier)

        if not channel_state:
            continue

        if channel.get_status(channel_state) != CHANNEL_STATE_OPENED:
            continue

        pending_transfers = channel.get_number_of_pending_transfers(channel_state.our_state)
        if pending_transfers >= MAXIMUM_PENDING_TRANSFERS:
            continue

        distributable = channel.get_distributable(
            channel_state.our_state,
            channel_state.partner_state,
        )
        if transfer_amount > distributable:
            continue

        if channel.is_valid_amount(channel_state.our_state, transfer_amount):
            return channel_state

    return None