log/api.go
func Debugf(ctx context.Context, format string, args ...interface{}) {
	internal.Logf(ctx, 0, format, args...)
}
func Debugf(ctx context.Context, format string, args ...interface{}) {
	internal.Logf(ctx, 0, format, args...)
}
// Debugf formats its arguments according to the format, analogous to fmt.Printf,
// and records the text as a log message at Debug level. The message will be associated
// with the request linked with the provided context.