R6 classes, cloning, and a simple way of modifying the elements of the nested R6 object - r

Question

I am developing a structure of R6 classes. The idea is to have a big R6 class collecting many small objects of other R6 class types. The big object is the input to a function.
The point is that I would like to make it simple for users to modify the small objects within the big by developing R6 methods in the public object that would facilitate this.
Let me explain on the following example:
ClassOne object is one of the small objects:
> ClassOne = R6::R6Class(
+ "ClassOne",
+
+ public = list(
+ element = numeric(),
+
+ initialize = function() {
+ self$element <- 1
+ },
+
+ set_element = function(value) {
+ if (!missing(value)) {
+ self$element <- value
+ }
+ }
+
+ )
+ )
ClassTwo object is the big object that contains as self$class_one_element an object of class ClassOne.
> ClassTwo = R6::R6Class(
+ "ClassTwo",
+
+ public = list(
+
+ class_one_element = list(),
+
+ initialize = function() {
+ self$class_one_element = ClassOne$new()
+ },
+
+ get_class_one = function() {
+ self$class_one_element$clone()
+ }
+ )
+ )
Once the ClassTwo object is initiated:
> ct = ClassTwo$new()
> ct$class_one_element$element
[1] 1
the method get_class_one is cloning the whole self$class_one_element:
> ct_co = ct$get_class_one()
The method set_element is used to modify the small object:
> ct_co$set_element(2)
> ct_co$element
[1] 2
but despite the application of deep cloning, this operation is modifying only the element in the small object ct_co and not the corresponding element in the big object:
> ct$class_one_element$element
[1] 1
THE QUESTION: How to rewrite the ClassTwo (I guess) so that the sequence:
> ct = ClassTwo$new()
> ct_co = ct$get_class_one()
> ct_co$set_element(2)
is modifying ct$class_one_element$element as well?
I would greatly appreciate your suggestions!