Function empty

include/behaviortree_cpp/contrib/json.hpp:14002–14005

@brief return whether pointer points to the root document @sa https://json.nlohmann.me/api/json_pointer/empty/

    /// @brief return whether pointer points to the root document
    /// @sa https://json.nlohmann.me/api/json_pointer/empty/
    bool empty() const noexcept
    {
        return reference_tokens.empty();
    }

  private:
    /*!