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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 get_relationship(self, attribute):
 """ Returns the domain relationship object for the given resource attribute. """

        rel = self.__relationships.get(attribute.entity_attr)
        if rel is None:
            rel = LazyDomainRelationship(self, attribute,
                                         direction=
                                            self.relationship_direction)
            self.__relationships[attribute.entity_attr] = rel
        return rel