lgr comes with the following predefined log levels that are identical to
the log levels of log4j.
| Level | Name | Description | 
| 0 | off | A log level of 0/off tells a Logger or Appender to suspend all logging | 
| 100 | fatal | Critical error that leads to program abort. Should always indicate a stop()or similar | 
| 200 | error | A severe error that does not trigger program abort | 
| 300 | warn | A potentially harmful situation, like warning() | 
| 400 | info | An informational message on the progress of the application | 
| 500 | debug | Finer grained informational messages that are mostly useful for debugging | 
| 600 | trace | An even finer grained message than debug |