def _update_subinstance(self, name, subform):
old_subinstance = getattr(self.instance, name)<EOL>new_subinstance = subform.update_instance()<EOL>if old_subinstance is None and not new_subinstance.is_empty():<EOL><INDENT>setattr(self.instance, name, new_subinstance)<EOL><DEDENT>if old_subinstance is not None and new_subinstance.is_empty():<EOL><INDENT>delattr(self.instance, name)<EOL><DEDENT>
Save bound data for a single subform into the XmlObject model
        instance.