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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 get_parent_vault_nodes(self):
 """Gets the parents of this vault. return: (osid.authorization.VaultNodeList) - the parents of this vault *compliance: mandatory -- This method must be implemented.* """

        parent_vault_nodes = []
        for node in self._my_map['parentNodes']:
            parent_vault_nodes.append(VaultNode(
                node._my_map,
                runtime=self._runtime,
                proxy=self._proxy,
                lookup_session=self._lookup_session))
        return VaultNodeList(parent_vault_nodes)