Hamamatsu NDPI missing some levels

[ap--]

ts_slide = TiffSlide('OS-3.ndpi'), os_slide = OpenSlide('OS-3.ndpi')

    def test_level_count(ts_slide, os_slide):
>       assert ts_slide.level_count == os_slide.level_count
E       assert 10 == 13
E         +10
E         -13

[ap--]

This is really minor. TiffSlide levels are a strict subset of the OpenSlide levels.