def test_add_already_added(self):
        prio_set_list = event._PrioritizedSetList()
        obj = object()
        prio_set_list.add(0, obj)

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(0, obj)
        excinfo.match(r"has already been added")

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(1, obj)
        excinfo.match(r"has already been added")
def __calculate_initial_clusters(self, centers):
        """!
        @brief Calculate Euclidean distance to each point from the each cluster. 
        @brief Nearest points are captured by according clusters and as a result clusters are updated.