/// If some channels aren't announced, it may be useful to fill in a first_hops with the
/// results from a local ChannelManager::list_usable_channels() call. If it is filled in, our
/// (this Router's) view of our local channels will be ignored, and only those in first_hops
/// If some channels aren't announced, it may be useful to fill in a first_hops with the
/// results from a local ChannelManager::list_usable_channels() call. If it is filled in, our
/// (this Router's) view of our local channels will be ignored, and only those in first_hops