code: def previous(self, field):
          
  
          # handle deferred fields that have not yet been loaded from the database
          if self.instance.pk and field in self.deferred_fields and field not in self.saved_data:
  
              # if the field has not been assigned locally, simply fetch and un-defer the value
              if field not in self.instance.__dict__:
                  self.get_field_value(field)
  
              # if the field has been assigned locally, store the local value, fetch the database value,
              # store database value to saved_data, and restore the local value
              else:
                  current_value = self.get_field_value(field)
                  self.instance.refresh_from_db(fields=[field])
                  self.saved_data[field] = deepcopy(self.get_field_value(field))
                  setattr(self.instance, self.field_map[field], current_value)
  
          return self.saved_data.get(field)
docs: Returns currently saved value of given field