code: func (s *CA) GetCertAuthority(id services.CertAuthID, loadSigningKeys bool, opts ...services.MarshalOption) (services.CertAuthority, error) {
  	if err := id.Check(); err != nil {
  		return nil, trace.Wrap(err)
  	}
  	item, err := s.Get(context.TODO(), backend.Key(authoritiesPrefix, string(id.Type), id.DomainName))
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	ca, err := services.GetCertAuthorityMarshaler().UnmarshalCertAuthority(
  		item.Value, services.AddOptions(opts, services.WithResourceID(item.ID), services.WithExpires(item.Expires))...)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	if err := ca.Check(); err != nil {
  		return nil, trace.Wrap(err)
  	}
  	setSigningKeys(ca, loadSigningKeys)
  	return ca, nil
  }
docs: // GetCertAuthority returns certificate authority by given id. Parameter loadSigningKeys
  // controls if signing keys are loaded