code: def test_merge_3(self):
      template3 = go.layout.Template(
          layout={"margin": {"l": 0, "r": 0}}
      )
      result = pio.templates.merge_templates(
          self.template1, self.template2, template3
      )
  
      expected = self.expected1_2
      expected.update(template3)
      self.assertEqual(result, expected)
  
      # Make sure input templates weren't modified
      self.assertEqual(self.template1, self.template1_orig)
      self.assertEqual(self.template2, self.template2_orig)
  
imports: import copy
  from unittest import TestCase
  import pytest
  import plotly.io
  import plotly.graph_objs
  from plotly.tests.utils import TestCaseNoTemplate
label_desc: Use image node_id 5 for calling the TestMergeTemplates obj's underlying member method code with example usage: obj.test_merge_3() without return types