in src/visual.ts [144:150]
private static getPropertyValue<T>(objects: DataViewObjects, dataViewObjectPropertyReference: DataViewObjectPropertyReference<T>): T {
let object;
if (objects) {
object = objects[dataViewObjectPropertyReference.propertyIdentifier.objectName];
}
return Visual.getValue(object, dataViewObjectPropertyReference.propertyIdentifier.propertyName, dataViewObjectPropertyReference.defaultValue);
}