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