log

type Formatter interface {
	// Next returns a new instance of formatter for sub-logger
	Next() Formatter

	// Format formats log message
	Format(format string, args ...interface{}) string

	// WrapString wraps log string
	WrapString(str string) string

	// WrapMultiline wraps multiline string
	WrapMultiline(str string) (out string)
}

type Writer interface {
	// Write writes a message to log with specified level
	Write(level int, message string)
}