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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 dangling(self):
 """ List of entities that aren't included in a closed path Returns dangling: (n,) int, index of self.entities """

        if len(self.paths) == 0:
            return np.arange(len(self.entities))
        else:
            included = np.hstack(self.paths)
        dangling = np.setdiff1d(np.arange(len(self.entities)),
                                included)
        return dangling