code: public static PrintStream wrapAndDumpWhenContains(PrintStream source, String trigger) {
  		StringPrinter wrapped = new StringPrinter(StringPrinter.stringsToLines(perLine -> {
  			source.println(perLine);
  			if (perLine.contains(trigger)) {
  				dump("Triggered by " + trigger);
  			}
  		}));
  		return wrapped.toPrintStream();
  	}
docs: Returns a PrintStream which will redirect all of its output to the source PrintStream. If
  the trigger string is passed through the wrapped PrintStream, then it will dump the
  stack trace of the call that printed the trigger.
  
  @param source
  the returned PrintStream will delegate to this stream
  @param trigger
  the string which triggers a stack dump
  @return a PrintStream with the above properties