code: func (r *PCPRegistry) AddInstanceDomainByName(name string, instances []string) (InstanceDomain, error) {
  	if r.HasInstanceDomain(name) {
  		return nil, errors.New("The InstanceDomain already exists for this registry")
  	}
  
  	indom, err := NewPCPInstanceDomain(name, instances)
  	if err != nil {
  		return nil, err
  	}
  
  	err = r.AddInstanceDomain(indom)
  	if err != nil {
  		return nil, err
  	}
  
  	return indom, nil
  }
docs: // AddInstanceDomainByName adds an instance domain using passed parameters