code: def test_frame_number_to_filepath(self):
      file_names_vid4 = VideoDataset._frame_number_to_filepaths(
          MOCK_VIDEO_IDS[3],
          get_flat_video_frames("testdirectory", "jpg"),
          MOCK_VIDEO_INFOS,
      )
      file_path = file_names_vid4[100]
      self.assertEqual(
          file_path,
          f"testdirectory/{MOCK_VIDEO_IDS[3]}/frame_0000000101.jpg",
      )
      with self.assertRaises(IndexError):
          file_path = file_names_vid4[10000]
      file_path = file_names_vid4[-1]
      self.assertEqual(
          file_path,
          f"testdirectory/{MOCK_VIDEO_IDS[3]}/frame_0000001530.jpg",
      )
  
      file_names_vid2 = VideoDataset._frame_number_to_filepaths(
          MOCK_VIDEO_IDS[1],
          get_flat_video_frames("testdirectory2", "png"),
          MOCK_VIDEO_INFOS,
      )
      file_path = file_names_vid2[0]
      self.assertEqual(
          file_path,
          f"testdirectory2/{MOCK_VIDEO_IDS[1]}/frame_0000000002.png",
      )
      file_path = file_names_vid2[2999]
      self.assertEqual(
          file_path,
          f"testdirectory2/{MOCK_VIDEO_IDS[1]}/frame_0000003001.png",
      )
      with self.assertRaises(IndexError):
          file_path = file_names_vid2[3000]
  
file_path: pytorchvideo/tests/test_data_dataset_manifest_utils.py
imports: import unittest
  import unittest.mock
  from pytorchvideo.data.dataset_manifest_utils import EncodedVideoInfo, VideoDataset, VideoFrameInfo, VideoInfo
  from utils import get_flat_video_frames, MOCK_VIDEO_IDS, MOCK_VIDEO_INFOS
label_desc: Use image node_id 4 for calling the TestDatasetManifestUtils obj's underlying member method code with example usage: obj.test_frame_number_to_filepath() without return types