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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 assert_powernode(self, name:str) -> None or ValueError: """Do nothing if given name refers to a powernode in given graph. Raise a ValueError in any other case. """

        if name not in self.inclusions:
            raise ValueError("Powernode '{}' does not exists.".format(name))
        if self.is_node(name):
            raise ValueError("Given name '{}' is a node.".format(name))