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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_all_relationships(self):
 """Return all relationships seen in GO Dag subset."""

        relationships_all = set()
        for goterm in self.go2obj.values():
            if goterm.relationship:
                relationships_all.update(goterm.relationship)
            if goterm.relationship_rev:
                relationships_all.update(goterm.relationship_rev)
        return relationships_all