code: def test_diff_dirty(tmp_dir, scm, dvc, run_copy_metrics):
      (tmp_dir / "metric_t.json").dump(
          [{"y": 2}, {"y": 3}], sort_keys=True
      )
      run_copy_metrics(
          "metric_t.json",
          "metric.json",
          plots=["metric.json"],
          name="train",
          commit="init",
      )
  
      metric_head = [{"y": 3}, {"y": 5}]
      (tmp_dir / "metric_t.json").dump_json(metric_head, sort_keys=True)
      dvc.reproduce()
      scm.add(["dvc.lock"])
      scm.commit("second")
  
      metric_1 = [{"y": 5}, {"y": 6}]
      (tmp_dir / "metric_t.json").dump_json(metric_1, sort_keys=True)
      dvc.reproduce()
  
      props = {"fields": ["y"]}
      diff_result = dvc.plots.diff(props=props)
  
      assert (
          get_plot(diff_result, "workspace", file="metric.json")
          == metric_1
      )
      assert get_plot(
          diff_result,
          "workspace",
          "definitions",
          file="",
          endkey="data",
      ) == {"metric.json": props}
      assert (
          get_plot(diff_result, "HEAD", file="metric.json")
          == metric_head
      )
      assert get_plot(
          diff_result, "HEAD", "definitions", file="", endkey="data"
      ) == {"metric.json": props}
  
      metric_2 = [{"y": 7}, {"y": 8}]
      (tmp_dir / "metric.json").dump_json(metric_2, sort_keys=True)
  
      diff_result = dvc.plots.diff(props=props)
      assert (
          get_plot(diff_result, "workspace", file="metric.json")
          == metric_2
      )
      assert get_plot(
          diff_result,
          "workspace",
          "definitions",
          file="",
          endkey="data",
      ) == {"metric.json": props}
  
      assert (
          get_plot(diff_result, "HEAD", file="metric.json")
          == metric_head
      )
      assert get_plot(
          diff_result,
          "workspace",
          "definitions",
          file="",
          endkey="data",
      ) == {"metric.json": props}
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_diff_dirty(tmp_dir, scm, dvc, run_copy_metrics) without return types