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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 choice(self, obj):
 """ Overloads the choice method to add the position of the object in the tree for future sorting. """

        tree_id = getattr(obj, self.queryset.model._mptt_meta.tree_id_attr, 0)
        left = getattr(obj, self.queryset.model._mptt_meta.left_attr, 0)
        return super(MPTTModelChoiceIterator,
                     self).choice(obj) + ((tree_id, left),)