code: def test_all_sparktext():
      """Test all character sparktext"""
      chart = Line()
      chart.add("_", range(8))
      assert chart.render_sparktext() == "▁▂▃▄▅▆▇█"
  
file_path: pygal/pygal/test/test_sparktext.py
imports: from pygal import Bar, Line
label_desc: Use image node_id 2 for calling a global function with example usage: test_all_sparktext() without return types