[boost] [log] Yet more questions for Andrey: formatting severity

By default, severity is printed as integer. What's the easiest way to print the corresponding string (e.g. "info" for severity 0, "warn" for severity 1, and so on)? I tried defining operator<< for my severity enum, but attr<severity_level> doesn't work; that is, the output operator doesn't get invoked (I assume because attribute "Severity" is internally of type "int" and not of my enum type). Thanks a lot! Igor