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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_predecessors(self, cfgnode):
 """ Get all predecessors of a specific node on the control flow graph. :param CFGNode cfgnode: The CFGNode object :return: A list of predecessors in the CFG :rtype: list """

        s = set()
        for child, parent in networkx.dfs_predecessors(self.graph, cfgnode).items():
            s.add(child)
            s.add(parent)
        return list(s)