code: def test_ordered_set():
      s = utils.OrderedSet()
      s.add("a", "b", "c")
      assert_equal(s.items, ["a", "b", "c"])
  
imports: from nose.tools import assert_equal
  from pyecharts.commons import utils
  from pyecharts.datasets import EXTRA
label_desc: Use image node_id 4 for calling a global function with example usage: test_ordered_set() without return types