public static object field_of_expanded (object root_object, FieldInfo [] a_fields, FieldInfo a_field)
// Get value of `a_field', an attribute reachable from `root_object' using `a_fields' as a path to
// reach it.
{
TypedReference t = TypedReference.MakeTypedReference(root_object, a_fields);
return a_field.GetValueDirect(t);
}