code: def test_empty_lists_with_nones(Chart):
      """Test chart rendering with a None filled serie"""
      chart = Chart()
      chart.add("A", [None, None])
      chart.add("B", [None, 4, 4])
      q = chart.render_pyquery()
      assert len(q(".legend")) == 2
  
imports: import io
  import os
  import uuid
  import pytest
  import pygal
  from pygal.graph.map import BaseMap
  from pygal.test import make_data
  from pygal.util import cut
label_desc: Use image node_id 6 for calling a global function with example usage: test_empty_lists_with_nones(Chart) without return types