code: def test_image_spec(self, image_data, cmap, norm, expected):
      image_data.flags.writeable = False
      # spec = geom_imshow(image_data, extent=_extent)
      spec = geom_imshow(image_data, cmap=cmap, norm=norm, alpha=0.5)
      assert spec.as_dict() == expected
  
imports: import numpy
  import pytest
  from lets_plot.plot.geom_imshow_ import geom_imshow
  from test_geom_imshow_util import _image_spec, _image_bbox
label_desc: Use image node_id 1 for calling the Test obj's underlying member method code with example usage: obj.test_image_spec(image_data, cmap, norm, expected) without return types