void pop(Map<Integer, Bubble> allBubbles) {
    LOGGER.info("Bubble {} popped at ({},{})!", this.id, this.coordinateX, this.coordinateY);
    allBubbles.remove(this.id);
  }
@Test
  void popTest() {
    var b1 = new Bubble(10, 10, 1, 2);
    var b2 = new Bubble(0, 0, 2, 2);
    var bubbles = new HashMap<Integer, Bubble>();
    bubbles.put(1, b1);
    bubbles.put(2, b2);
    b1.pop(bubbles);
    //after popping, bubble no longer in hashMap containing all bubbles
    assertNull(bubbles.get(1));
    assertNotNull(bubbles.get(2));
  }