docs: public void setChildPropertySetter(final Object childPropertySetter) {
          if (childPropertySetter instanceof ChildPropertySetter) {
              this.childPropertySetter = (ChildPropertySetter) childPropertySetter;
          } else if (childPropertySetter instanceof Closure) {
              final ObjectGraphBuilder self = this;
              this.childPropertySetter = new ChildPropertySetter() {
                  public void setChild(Object parent, Object child, String parentName,
                                       String propertyName) {
                      Closure cls = (Closure) childPropertySetter;
                      cls.setDelegate(self);
                      cls.call(parent, child, parentName, propertyName);
                  }
              };
          } else {
              this.childPropertySetter = new DefaultChildPropertySetter();
          }
      }