value_type& value() const;
Returns: A reference to the value_type subobject in the container_node_type object pointed to by ptr_.
key_type& key() const;
Returns: A non-const reference to the key_type member of the value_type subobject in the container_node_type object pointed to by ptr_.
mapped_type& mapped() const;
Returns: A reference to the mapped_type member of the value_type subobject in the container_node_type object pointed to by ptr_.
allocator_type get_allocator() const;
explicit operator bool() const noexcept;
bool empty() const noexcept;