Custom loggers must implement this one method.
Log message severities.
Logs a message.
Logs a formatted message.
Logs an INFO message.
Logs an INFO message, with formatting.
Logs a DEBUG message, with formatting.
Logs a DEBUG message, with formatting.
Logs a WARNING message, with formatting.
Logs a WARNING message, with formatting.
Logs an ERROR message, with formatting.
Logs an ERROR message, with formatting.
Output log messages in a file.