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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 domain_relationship(self):
 """ Returns a domain relationship equivalent with this resource relationship. """

        if self.__domain_relationship is None:
            ent = self.relator.get_entity()
            self.__domain_relationship = \
                    self.descriptor.make_relationship(ent)
        return self.__domain_relationship