Return the input $value unchanged and, if $label is the name of
an enabled server event, emit that server event to the server log
ErrorLog.txt) with $value as its data.
|$value||The values to trace.|
|$label||A string label for the trace output.|
fn.trace("This is a trace event.", "MY TRACE EVENT") => If MY TRACE EVENT is defined as an enabled trace event in the Diagnostics page of the Admin interface, then a message similar to the following is added to the ErrorLog.txt file: 2015-03-20 17:56:09.346 Info: [Event:id=MY TRACE EVENT] This is a trace event.