A specialised invariant violation for entities whose lifecycle is a state machine. Kept distinct because it is by far the most common shape of rule in this domain: a physical copy of a book moves through legal states only.
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Indicates whether the argument provided is a built-in Error instance or not.
A specialised invariant violation for entities whose lifecycle is a state machine. Kept distinct because it is by far the most common shape of rule in this domain: a physical copy of a book moves through legal states only.