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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 _init_relationships(self, relationships_arg):
 """Return a set of relationships found in all subset GO Terms."""

        if relationships_arg:
            relationships_all = self._get_all_relationships()
            if relationships_arg is True:
                return relationships_all
            else:
                return relationships_all.intersection(relationships_arg)
        return set()