def METHOD_NAME(self):
    # Create some observations.
    obs = list([])
    obs2 = list([])
    obs_total = list([])
    obs.append(Vector3d(1.0, 1.0, 0.0))
    obs.append(Vector3d(1.1, 1.0, 0.0))
    obs.append(Vector3d(1.2, 1.0, 0.0))
    obs.append(Vector3d(1.3, 1.0, 0.0))
    obs.append(Vector3d(1.4, 1.0, 0.0))
    obs2.append(Vector3d(5.0, 1.0, 0.0))
    obs2.append(Vector3d(5.1, 1.0, 0.0))
    obs2.append(Vector3d(5.2, 1.0, 0.0))
    obs2.append(Vector3d(5.3, 1.0, 0.0))
    obs2.append(Vector3d(5.4, 1.0, 0.0))
    for elem in obs:
        obs_total.append(elem)
    for elem in obs2:
        obs_total.append(elem)
    # Initialize Kmeans with two partitions.
    kmeans = Kmeans(obs)
    kmeans.append_observations(obs2)
    obs_copy = kmeans.observations()
    for i in range(len(obs_copy)):
        self.assertEqual(obs_total[i], obs_copy[i])
    # Append an empty vector.
    emptyVector = []
    self.assertFalse(kmeans.append_observations(emptyVector))