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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 clear(self):
 """Clear variable nodes for next computation."""

        for n in self.nodes():
            if self.nodes[n]["type"] == "variable":
                self.nodes[n]["value"] = None
            elif self.nodes[n]["type"] == "function":
                self.nodes[n]["func_visited"] = False