kvlog/writer.go
func (w *Writer) SetLevel(level string, effect string) {
	levels := w.Levels()
	levels[level] = effect
	w.SetLevels(levels)
}
func (w *Writer) SetLevel(level string, effect string) {
	levels := w.Levels()
	levels[level] = effect
	w.SetLevels(levels)
}
// SetLevel sets an individual level and its associated display effect.