code: func (tc *TeleportClient) AddTrustedCA(ca services.CertAuthority) error {
  	err := tc.LocalAgent().AddHostSignersToCache(auth.AuthoritiesToTrustedCerts([]services.CertAuthority{ca}))
  	if err != nil {
  		return trace.Wrap(err)
  	}
  
  	// only host CA has TLS certificates, user CA will overwrite trusted certs
  	// to empty file if called
  	if ca.GetType() == services.HostCA {
  		err = tc.LocalAgent().SaveCerts(auth.AuthoritiesToTrustedCerts([]services.CertAuthority{ca}))
  		if err != nil {
  			return trace.Wrap(err)
  		}
  	}
  
  	return nil
  }
docs: // Adds a new CA as trusted CA for this client, used in tests