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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 fill_parentidid2obj_r0(self, id2obj, child_obj):
 """Fill id2obj with all parent key item IDs and their objects."""

        for parent_obj in child_obj.parents:
            if parent_obj.item_id not in id2obj:
                id2obj[parent_obj.item_id] = parent_obj
                self.fill_parentidid2obj_r0(id2obj, parent_obj)