code: def test_class_map_background(classes, background):
      class_map = ClassMap(classes, background=background)
      assert class_map.get_by_id(0) == background
      assert class_map.get_by_name(background) == 0
      assert class_map.get_by_id(1) == "a"
      assert class_map.get_by_name("a") == 1
  
imports: import pytest
  from icevision.all import *
label_desc: Use image node_id 3 for calling a global function with example usage: test_class_map_background(classes, background) without return types