code: def test_reference() -> None:
      assert imagelosses.SumAbsoluteDifferences.REQUIRES_REFERENCE
      assert not imagelosses.Blur.REQUIRES_REFERENCE
      assert not imagelosses.Koncept512.REQUIRES_REFERENCE
      assert not imagelosses.Brisque.REQUIRES_REFERENCE
      assert (
          len(
              [
                  loss
                  for loss in imagelosses.registry.values()
                  if loss.REQUIRES_REFERENCE
              ]
          )
          == 5
      )
      assert (
          len(
              [
                  loss
                  for loss in imagelosses.registry.values()
                  if not loss.REQUIRES_REFERENCE
              ]
          )
          == 3
      )
  
file_path: nevergrad/nevergrad/functions/images/test_imagelosses.py
imports: from pathlib import Path
  import PIL.Image
  import numpy
  import pytest
  from nevergrad.functions.images import imagelosses
label_desc: Use image node_id 1 for calling a global function with example usage: test_reference() without return types