in src/main/java/org/apache/sling/scripting/xproc/xpl/impl/AbstractXplElementImpl.java [170:181]
private Field getChildField(XplElement child) {
Class<?> currentClass = this.getClass();
Field[] declaredFields = currentClass.getDeclaredFields();
for (Field declaredField : declaredFields) {
if (declaredField.getType().isAssignableFrom(child.getClass())) {
return declaredField;
}
}
return null;
}