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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def record_id(self, record, type_=None, selector=None):
 """Retrieve an object identifier from the given record; if it is an alien class, and the type is provided, then use duck typing to get the corresponding fields of the alien class."""

        pk = record_id(record, type_, selector, self.normalize_object_slot)
        return pk