code: def test_si_units():
      """Test that our scalings actually produce SI units."""
      scalings = _handle_default("scalings", None)
      units = _handle_default("units", None)
      # Add a bad one to test that we actually detect it
      assert "csd_bad" not in scalings
      scalings["csd_bad"] = 1e5
      units["csd_bad"] = "V/m²"
      assert set(scalings) == set(units)
  
      for key, scale in scalings.items():
          if key == "csd_bad":
              with pytest.raises(
                  KeyError, match="is not a channel type"
              ):
                  want_scale = _get_scaling(key, units[key])
          else:
              want_scale = _get_scaling(key, units[key])
              assert_allclose(scale, want_scale, rtol=1e-12)
  
imports: from copy import deepcopy
  import pytest
  from numpy.testing import assert_allclose
  from mne.defaults import _handle_default
  from mne.io.base import _get_scaling
label_desc: Use image node_id 2 for calling a global function with example usage: test_si_units() without return types