Return the state of settled channels in a token network.

def get_channelstate_settled(
        chain_state: ChainState,
        payment_network_id: PaymentNetworkID,
        token_address: TokenAddress,
) -> List[NettingChannelState]:
    """Return the state of settled channels in a token network."""
    return get_channelstate_filter(
        chain_state,
        payment_network_id,
        token_address,
        lambda channel_state: channel.get_status(channel_state) == CHANNEL_STATE_SETTLED,
    )