code: def test_invalid_file(self):
      set_video_backend("video_reader")
      with pytest.raises(RuntimeError):
          io.read_video("foo.mp4")
  
      set_video_backend("pyav")
      with pytest.raises(RuntimeError):
          io.read_video("foo.mp4")
  
imports: import collections
  import math
  import os
  from fractions import Fraction
  import numpy
  import pytest
  import torch
  import torchvision.io
  from common_utils import assert_equal
  from numpy.random import randint
  from pytest import approx
  from torchvision import set_video_backend
  from torchvision.io import _HAS_VIDEO_OPT
label_desc: Use image node_id 23 for calling the TestVideoReader obj's underlying member method code with example usage: obj.test_invalid_file() without return types