/// the corresponding channel for the event, as we only have access to the `channel_id` during
/// the handling of the events.
///
+ /// Note that no consistency guarantees are made about the existence of a peer with the
+ /// `counterparty_node_id` in our other maps.
+ ///
/// TODO:
/// The `counterparty_node_id` isn't passed with `MonitorEvent`s currently. To pass it, we need
/// to make `counterparty_node_id`'s a required field in `ChannelMonitor`s, which unfortunately