Method: (PRINT-OBJECT PERSISTENT-DATA T)

Source

(defmethod print-object ((object persistent-data) stream)
  (print-unreadable-object (object stream :type t :identity nil)
    (format stream "#~D~@[ with transaction id ~D~]"
            (slot-value object 'object-id)
            (and (slot-boundp object 'transaction-id)
                 (slot-value object 'transaction-id)))))