Hum? What assignment into the object? Where I'd typically see taking a `const std::shared_ptr<> &` to signal "retaining ownership" would be something like this:

    class Foo {
    public:
        void AppendChild(const std::shared_ptr<Foo> &x) {
            children_.emplace_back(x);
        }
    private:
        std::vector<std::shared_ptr<Foo>> children_;
    };