The Warning module contains a single method
named warn, and the module extends
itself, making Warning.warn
available. #warn is called for all warnings
issued by Ruby. By default, warnings are printed to $stderr.
By overriding #warn, you can change how warnings are handled by Ruby, either filtering some warnings, and/or outputting warnings somewhere other than $stderr. When #warn is overridden, super can be called to get the default behavior of printing the warning to $stderr.