code: def test_check_orig_units():
      """Test the checking of original units."""
      orig_units = dict(
          FC1="nV", Hfp3erz="n/a", Pz="uV", greekMu="μV", microSign="µV"
      )
      orig_units = _check_orig_units(orig_units)
      assert orig_units["FC1"] == "nV"
      assert orig_units["Hfp3erz"] == "n/a"
      assert orig_units["Pz"] == "µV"
      assert orig_units["greekMu"] == "µV"
      assert orig_units["microSign"] == "µV"
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_check_orig_units() without return types