def addPolicyURI(self, policy_uri):
        if policy_uri not in self.preferred_auth_policies:
            self.preferred_auth_policies.append(policy_uri)
Clusters objects in `dismat` using spectral clustering. 
dataset/ETHPy150Open CollabQ/CollabQ/openid/extensions/pape.py/Request.addPolicyURI--crossover with--dataset/ETHPy150Open inpho/vsm/vsm/extensions/clustering/manifold.py/Manifold.SpectralClustering