def effective_owner_property_value
      self.class.owner_properties.detect_value do |op|
        ref = send(op.attribute)
        [op, ref] if ref
      end
    end
def effective_owner_property_value
      self.class.owner_properties.detect_value do |op|
        ref = send(op.attribute)
        [op, ref] if ref
      end
    end
Returns the (property, value) pair for which there is an owner reference, or nil if
 this domain object does not reference an owner.

 @return [(Property, Resource), nil] the owner (property, value) pair