Contract for id() documented in JanusGraphElement is not respected

In the java doc for id() method in JanusGraphElement interface, it is stated that the id() should throw IllegalStateException if entity does not (yet) have a unique identifier:
https://github.com/JanusGraph/janusgraph/blob/548d7ad64f6663f6f4b80178601fedf73d6eac72/janusgraph-core/src/main/java/org/janusgraph/core/JanusGraphElement.java#L48-L65

but in AbstractVertex class, id() method can return a negative value, if the transaction (within which this vertex is created) is not committed yet. See

https://github.com/JanusGraph/janusgraph/blob/548d7ad64f6663f6f4b80178601fedf73d6eac72/janusgraph-core/src/main/java/org/janusgraph/graphdb/vertices/AbstractVertex.java#L78-L81

and

https://github.com/JanusGraph/janusgraph/blob/548d7ad64f6663f6f4b80178601fedf73d6eac72/janusgraph-core/src/main/java/org/janusgraph/graphdb/internal/AbstractElement.java#L26-L36

Thus I think maybe the java doc for id() method in the base interface JanusGraphElement should be updated. Please correct me if I miss something.

Start by comparing the id() contract in janusgraph-core/src/main/java/org/janusgraph/core/JanusGraphElement.java with the implementations in graphdb/vertices/AbstractVertex.java and graphdb/internal/AbstractElement.java. Confirm how an uncommitted vertex is represented and whether the interface documentation or implementation conflicts with that behavior. Done means the documented contract accurately matches the confirmed behavior.

Written by the indexing model from the issue text.