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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 tree(self):
 """ Deserialize and return a labeled syntax tree. The tree data may be a standalone datum, or embedded in the derivation. """

        tree = self.get('tree')
        if isinstance(tree, stringtypes):
            tree = SExpr.parse(tree).data
        elif tree is None:
            drv = self.get('derivation')
            if isinstance(drv, dict) and 'label' in drv:
                def _extract_tree(d):
                    t = [d.get('label', '')]
                    if 'tokens' in d:
                        t.append([d.get('form', '')])
                    else:
                        for dtr in d.get('daughters', []):
                            t.append(_extract_tree(dtr))
                    return t
                tree = _extract_tree(drv)
        return tree