showLog function
Indicates that diagnostic log statements should be output. Typically, place this statement at the start of your program.
Expects an IO destination that is normally stdout, stderr or a file, as well as a Severity level.
// example
showLog(stdout, Severity.debug.value | Severity.warning.value);
Implementation
void showLog(IOSink outputTo, int level) {
_sink = outputTo;
_severity = level;
}