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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 _update_subinstance(self, name, subform):
 """Save bound data for a single subform into the XmlObject model instance."""

        old_subinstance = getattr(self.instance, name)
        new_subinstance = subform.update_instance()

        # if our instance previously had no node for the subform AND the
        # updated one has data, then attach the new node.
        if old_subinstance is None and not new_subinstance.is_empty():
            setattr(self.instance, name, new_subinstance)

        # on the other hand, if the instance previously had a node for the
        # subform AND the updated one is empty, then remove the node.
        if old_subinstance is not None and new_subinstance.is_empty():
            delattr(self.instance, name)