code: func (pis PeerIdentitySet) ByOrg() map[string]PeerIdentitySet {
  	m := make(map[string]PeerIdentitySet)
  	for _, id := range pis {
  		m[string(id.Organization)] = append(m[string(id.Organization)], id)
  	}
  	return m
  }
docs: // ByOrg sorts the PeerIdentitySet by organizations of its peers