code: def test_handle_default():
      """Test mutable default."""
      x = deepcopy(_handle_default("scalings"))
      y = _handle_default("scalings")
      z = _handle_default("scalings", dict(mag=1, grad=2))
      w = _handle_default("scalings", {})
      assert set(x.keys()) == set(y.keys())
      assert set(x.keys()) == set(z.keys())
      for key in x.keys():
          assert x[key] == y[key]
          assert x[key] == w[key]
          if key in ("mag", "grad"):
              assert x[key] != z[key]
          else:
              assert x[key] == z[key]
  
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 1 for calling a global function with example usage: test_handle_default() without return types