code: func NumPeers(raftConfig raft.Configuration) int {
  	var numPeers int
  	for _, server := range raftConfig.Servers {
  		if server.Suffrage == raft.Voter {
  			numPeers++
  		}
  	}
  	return numPeers
  }
docs: // NumPeers counts the number of voting peers in the given raft config.