code: def populate_audit_fields(self, event):
          
          event.updated = self._data
          event.original = self.get_original()._data
docs: Populates the the audit JSON fields with raw data from the model, so
          all changes can be tracked and diffed.
  
          Args:
              event (Event): The Event instance to attach the data to
              instance (fleaker.db.Model): The newly created/updated model