code: function(element, key, value, writeToDom) {
  
  			// DELETE
  			if (value === null) { // delete this property
  				var dataObject = getDataObject(element, key);
  				if (!dataObject) {
  					return;
  				}
  
  				var dataCount = element.getAggregation("customData").length;
  				if (dataCount == 1) {
  					element.destroyAggregation("customData", true); // destroy if there is no other data
  				} else {
  					element.removeAggregation("customData", dataObject, true);
  					dataObject.destroy();
  				}
  
  				// ADD or CHANGE
  			} else {
  				var CustomData = sap.ui.requireSync('sap/ui/core/CustomData');
  				var dataObject = getDataObject(element, key);
  				if (dataObject) {
  					dataObject.setValue(value);
  					dataObject.setWriteToDom(writeToDom);
  				} else {
  					var dataObject = new CustomData({key:key,value:value, writeToDom:writeToDom});
  					element.addAggregation("customData", dataObject, true);
  				}
  			}
  		}
docs: Contains the data modification logic