code: func (p *Peer) peerIsPresent(other *discoverd.Instance) bool {
  	// We should never even be asking whether we're present. If we need to do
  	// this at some point in the future, we need to consider we should always
  	// consider ourselves present or whether we should check the list.
  	if other.Meta[p.idKey] == p.id {
  		panic("peerIsPresent with self")
  	}
  	for _, peer := range p.Info().Peers {
  		if peer.Meta[p.idKey] == other.Meta[p.idKey] {
  			return true
  		}
  	}
  
  	return false
  }
docs: // Returns true if the given other peer appears to be present in the most
  // recently received list of present peers.