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Map nodes that have been extracted using the extract method are actually very versatile. We can extract nodes from a map instance and insert it into any other map or even multimap instance. It does also work between unordered_map and unordered_multimap instances, as well as with set/multiset and respective unordered_set/unordered_multiset.

In order to move items between different map/set structures, the types of key, value, and allocator need to be identical. Note that even if that is the case, we cannot move nodes from a map to an unordered_map, or from a set to an unordered_set.