@Nullable
  @Override
  public RoaringBitmap getNullBitmap(ValueBlock valueBlock) {
    return null;
  }
@Test
  public void testGetNullBitmapReturnsNull() {
    ExpressionContext isDistinctFromExpression =
        RequestContextUtils.getExpression(String.format(_expression, INT_SV_NULL_COLUMN, INT_SV_COLUMN));
    TransformFunction isDistinctFromTransformFunction =
        TransformFunctionFactory.get(isDistinctFromExpression, _dataSourceMap);

    Assert.assertNull(isDistinctFromTransformFunction.getNullBitmap(_projectionBlock));
  }