code: def test_node_tooltips_exist():
      da = pytest.importorskip("dask.array")
      pytest.importorskip("graphviz")
  
      a = da.ones((1000, 1000), chunks=(100, 100))
      b = a + a.T
      c = b.sum(axis=1)
  
      hg = c.dask
      g = to_graphviz(hg)
  
      for layer in g.body:
          if "label" in layer:
              assert "tooltip" in layer
              start = layer.find('tooltip="') + len('tooltip="')
              end = layer.find('"', start)
              tooltip = layer[start:end]
              assert len(tooltip) > 0
  
imports: from __future__ import annotations
  import os
  import threading
  import xml.etree.ElementTree
  from collections.abc import Set
  from concurrent.futures import ThreadPoolExecutor
  import pytest
  import dask
  from dask.blockwise import Blockwise, blockwise_token
  from dask.highlevelgraph import HighLevelGraph, Layer, MaterializedLayer, to_graphviz
  from dask.utils_test import inc
label_desc: Use image node_id 17 for calling a global function with example usage: test_node_tooltips_exist() without return types