code: def test_mpl_backend():
      """Check if the backend is correctly set for testing."""
      # only fail if matplotlib is otherwise available
      try:
          import matplotlib
      except ImportError:
          return
  
      assert matplotlib.get_backend() == "agg"
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_mpl_backend() without return types