code: def test_webagg_fallback(backend):
      pytest.importorskip("tornado")
      if backend == "nbagg":
          pytest.importorskip("IPython")
      env = dict(os.environ)
      if sys.platform != "win32":
          env["DISPLAY"] = ""
  
      env["MPLBACKEND"] = backend
  
      test_code = (
          "import os;"
          + f"assert os.environ['MPLBACKEND'] == '{backend}';"
          + "import matplotlib.pyplot as plt; "
          + "print(plt.get_backend());"
          f"assert '{backend}' == plt.get_backend().lower();"
      )
      ret = subprocess.call([sys.executable, "-c", test_code], env=env)
  
      assert ret == 0
  
imports: import subprocess
  import os
  import sys
  import pytest
  import matplotlib.backends.backend_webagg_core
label_desc: Use image node_id 1 for calling a global function with example usage: test_webagg_fallback(backend) without return types