code: def test_color_bins():
      assert color_bins(
          attr="pct_higher_ed",
          domain=[0, 20, 30, 40, 50, 60, 70],
          colors="PinkYl",
      ).serialize() == {
          "@@function": "colorBins",
          "attr": "pct_higher_ed",
          "domain": [0, 20, 30, 40, 50, 60, 70],
          "colors": "PinkYl",
          "nullColor": [204, 204, 204],
      }
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_color_bins() without return types