code: function(oRoadMap, oStep){
  		var oParent = oStep.getParent();
  		if (oParent === oRoadMap) {
  			return oParent.indexOfStep(oStep) + 1;
  		}
  
  		var iIdx = oParent.indexOfSubStep(oStep);
  
  		if (iIdx < 26) {
  			return String.fromCharCode(97 + iIdx);
  		} // Single character
  
  		//Double characters Substeps name are formed of 2 letters (e.g. "aa"). -> so overall 702 substeps possible
  		var firstCharIdx = Math.floor(iIdx / 26) - 1;
  		var secondCharIdx = iIdx % 26;
  		return String.fromCharCode(97 + firstCharIdx, 97 + secondCharIdx);
  	}
docs: Returns the name of the step according to its index in the aggregation (like "1", "a", "aa")