code: def test_adjointlayout_add_operator(self):
      layout1 = self.view3 << self.view2
      layout2 = self.view2 << self.view1
      self.assertEqual(type(layout1 + layout2), Layout)
  
imports: import numpy
  import pytest
  from holoviews import AdjointLayout, Element, GridSpace, HoloMap, Layout, NdLayout, Overlay
  from holoviews.element import Curve, HLine, Image
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 5 for calling the AdjointLayoutTest obj's underlying member method code with example usage: obj.test_adjointlayout_add_operator() without return types