The NullLogger will not process any log messages. 
In case of a log message with LogLevel.fatal nothing will happen.
import std.experimental.logger.core : LogLevel;
auto nl1 = new NullLogger(LogLevel.all);
nl1.info("You will never read this.");
nl1.fatal("You will never read this, either and it will not throw");
 The default constructor for the NullLogger. 
Independent of the parameter this Logger will never log a message.
| LogLevel lv | The LogLevelfor theNullLogger. By default theLogLevelforNullLoggerisLogLevel.all. | 
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Licensed under the Boost License 1.0.
    https://dlang.org/phobos/std_experimental_logger_nulllogger.html