def METHOD_NAME(self):
    dataset = Dataset({'x':self.xs, 'y':self.ys, 'z':self.zs},
                      kdims=['x', 'y'], vdims=['z'])
    reduced = Dataset({'x':self.xs, 'z':self.zs},
                      kdims=['x'], vdims=['z'])
    self.assertEqual(dataset.aggregate(['x'], np.mean).sort(), reduced.sort())