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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 set_object_acl(self, obj):
 """ Set object ACL on creation if not already present. """

        if not obj._acl:
            from nefertari_guards import engine as guards_engine
            acl = self._factory(self.request).generate_item_acl(obj)
            obj._acl = guards_engine.ACLField.stringify_acl(acl)