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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_all_nodes(self):
 """Returns a list of all nodes in this cluster as a mixed list of different node kinds. :return: list of :py:class:`Node` """

        nodes = self.nodes.values()
        if nodes:
            return reduce(operator.add, nodes, list())
        else:
            return []