a global variable / static logger in google script - spreadsheet

I'm working with several different GS-files (Google Script) to make and have a clear view on the code.

But I'm struggling to make the LOGGER of PeterHerrmann, available in several functions ... by making it a global variable.

I also tried to work with an initialise function ... and call it in the function where the logger is needed.

Most probably, I do something wrong.

So I created global variable :

var key01='14NgJC...'; // name of Google spreadsheet: Kopie van VIDEO
var key02='1xSn08...'; // name of Google spreadsheet: VIDEO
var selKey=key02;  // method 1 - via variable
var keySheet;      // method 2 - via properties
var Logger;

This is the init function : BUT doesn't seems to work when I uncomment it the function to call this function

function initLog(){
   //method 1 - key
   keySheet=key02;
   // used Google spreadsheet
   //method 2 - via properties
  PropertiesService.getScriptProperties().setProperty('keySpreadSheet', key02);
   selKey = PropertiesService.getScriptProperties().getProperty('keySpreadSheet');
   // Add one line to use BetterLog
   //Logger = BetterLog.useSpreadsheet(keySheet);
   //Logger = BetterLog.useSpreadsheet(selKey);
   //Now you can log and it will also log to the spreadsheet
   Logger.log("That's all you need to do");
   // Add one line to use BetterLog and log to a spreadsheet
   //method 1 - key
   Logger = BetterLog.useSpreadsheet(keySheet);
   //method 2 - via properties
   //Logger = BetterLog.useSpreadsheet(selKey);
}

And one of the (test) methods to use the LOGGER:

function myFunctionLog() {
  try {
    //initLog();
    // Add one line to use BetterLog and log to a spreadsheet
    // method 1 - key variable
    Logger = BetterLog.useSpreadsheet(keySheet);
    // method 2 - via properties
    //Logger = BetterLog.useSpreadsheet(selKey);
    //Now you can log and it will also log to the spreadsheet
    Logger.log("That's all you need to do -%s", "static logger");
    //Do more logging
    for (var i = 0; i < 5; i++) {
      var processingMessage = 'Processing ' + i;
    Logger.finest('This is inside my loop. i is %s', i );
  }
  //We're done
  Logger.log('The loop is done and i is now %s', i );
  } ...
  }
}

BetterLogger

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