public Sensor sensor(String name) {
        return this.sensor(name, Sensor.RecordingLevel.INFO);
    }
@Test
    public void testBadSensorHierarchy() {
        Sensor p = metrics.sensor("parent");
        Sensor c1 = metrics.sensor("child1", p);
        Sensor c2 = metrics.sensor("child2", p);
        assertThrows(IllegalArgumentException.class, () -> metrics.sensor("gc", c1, c2));
    }