No module named 'image_viewer'

[magamig]

When running the test with python test.py in Python 3.7.10, it throws the following error:

Traceback (most recent call last):
  File "test.py", line 6, in <module>
    import run_public
  File ".../UMA-MOT/UMA-TEST/run_public.py", line 5, in <module>
    from application_util import visualization
  File ".../UMA-MOT/UMA-TEST/application_util/visualization.py", line 6, in <module>
    from image_viewer import ImageViewer
ModuleNotFoundError: No module named 'image_viewer'

I've installed image_viewer with pip (although it was not on the requirements) - that didn't fix it.