code: def test_scale_array(mapper):
      assert mapper.scale_array is None
  
      with pytest.raises(KeyError, match="does not exist"):
          mapper.scale_array = "foo"
  
      scale_array = "array"
      mapper.scale_array = scale_array
      assert mapper.scale_array == scale_array
  
file_path: pyvista/tests/plotting/mappers/test_gaussian_mapper.py
imports: import pytest
  import pyvista
  from pyvista.plotting.mapper import PointGaussianMapper
label_desc: Use image node_id 5 for calling a global function with example usage: test_scale_array(mapper) without return types