code: def test_store_render_png(self):
      curve = Curve([1, 2, 3])
      data, metadata = Store.render(curve)
      mime_types = {"image/png"}
      self.assertEqual(set(data), mime_types)
  
imports: from holoviews import Curve, Store
  from holoviews.ipython import IPTestCase, notebook_extension
label_desc: Use image node_id 2 for calling the TestPNGDisplay obj's underlying member method code with example usage: obj.test_store_render_png() without return types