code: def setUp(self):
      self.format = ["html", "svg", "png"]
      super().setUp()
  
imports: from holoviews import Curve, Store
  from holoviews.ipython import IPTestCase, notebook_extension
label_desc: Use image node_id 1 for calling the TestCombinedDisplay obj's underlying member method code with example usage: obj.setUp() without return types