code: func (tc *TeleportClient) GetTrustedCA(ctx context.Context, clusterName string) ([]services.CertAuthority, error) {
  	// Connect to the proxy.
  	if !tc.Config.ProxySpecified() {
  		return nil, trace.BadParameter("proxy server is not specified")
  	}
  	proxyClient, err := tc.ConnectToProxy(ctx)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	defer proxyClient.Close()
  
  	// Get a client to the Auth Server.
  	clt, err := proxyClient.ClusterAccessPoint(ctx, clusterName, true)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  
  	// Get the list of host certificates that this cluster knows about.
  	return clt.GetCertAuthorities(services.HostCA, false)
  }
docs: // GetTrustedCA returns a list of host certificate authorities
  // trusted by the cluster client is authenticated with.