How to use the fvcore.common.file_io.PathManager.ls function in fvcore

PathManager.mkdirs(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.open(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.rm(self._tmpfile, foo="foo")  # type: ignore

        PathManager.set_strict_kwargs_checking(False)

        PathManager.copy(
            self._tmpfile, self._tmpfile, foo="foo"  # type: ignore
        )
        PathManager.exists(self._tmpfile, foo="foo")  # type: ignore
        PathManager.get_local_path(self._tmpfile, foo="foo")  # type: ignore
        PathManager.isdir(self._tmpfile, foo="foo")  # type: ignore
        PathManager.isfile(self._tmpfile, foo="foo")  # type: ignore
        PathManager.ls(self._tmpdir, foo="foo")  # type: ignore
        PathManager.mkdirs(self._tmpdir, foo="foo")  # type: ignore
        f = PathManager.open(self._tmpfile, foo="foo")  # type: ignore
        f.close()

        with open(os.path.join(self._tmpdir, "test_rm.txt"), "w") as f:
            rm_file = f.name
            f.write(self._tmpfile_contents)
            f.flush()
        PathManager.rm(rm_file, foo="foo")  # type: ignore

def test_ls(self):
        # Create some files in the tempdir to ls out.
        root_dir = os.path.join(self._tmpdir, "ls")
        os.makedirs(root_dir, exist_ok=True)
        files = sorted(["foo.txt", "bar.txt", "baz.txt"])
        for f in files:
            open(os.path.join(root_dir, f), "a").close()

        children = sorted(PathManager.ls(root_dir))
        self.assertListEqual(children, files)

        # Cleanup the tempdir
        shutil.rmtree(root_dir)

def test_bad_args(self):
        # TODO (T58240718): Replace with dynamic checks
        with self.assertRaises(ValueError):
            PathManager.copy(
                self._tmpfile, self._tmpfile, foo="foo"  # type: ignore
            )
        with self.assertRaises(ValueError):
            PathManager.exists(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.get_local_path(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.isdir(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.isfile(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.ls(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.mkdirs(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.open(self._tmpfile, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.rm(self._tmpfile, foo="foo")  # type: ignore

        PathManager.set_strict_kwargs_checking(False)

        PathManager.copy(
            self._tmpfile, self._tmpfile, foo="foo"  # type: ignore
        )
        PathManager.exists(self._tmpfile, foo="foo")  # type: ignore
        PathManager.get_local_path(self._tmpfile, foo="foo")  # type: ignore
        PathManager.isdir(self._tmpfile, foo="foo")  # type: ignore
        PathManager.isfile(self._tmpfile, foo="foo")  # type: ignore

with self.assertRaises(NotImplementedError):
            PathManager.copy(
                self._remote_uri, self._remote_uri, foo="foo"  # type: ignore
            )
        with self.assertRaises(NotImplementedError):
            PathManager.exists(self._remote_uri, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.get_local_path(
                self._remote_uri, foo="foo"  # type: ignore
            )
        with self.assertRaises(NotImplementedError):
            PathManager.isdir(self._remote_uri, foo="foo")  # type: ignore
        with self.assertRaises(NotImplementedError):
            PathManager.isfile(self._remote_uri, foo="foo")  # type: ignore
        with self.assertRaises(NotImplementedError):
            PathManager.ls(self._remote_uri, foo="foo")  # type: ignore
        with self.assertRaises(NotImplementedError):
            PathManager.mkdirs(self._remote_uri, foo="foo")  # type: ignore
        with self.assertRaises(ValueError):
            PathManager.open(self._remote_uri, foo="foo")  # type: ignore
        with self.assertRaises(NotImplementedError):
            PathManager.rm(self._remote_uri, foo="foo")  # type: ignore

        PathManager.set_strict_kwargs_checking(False)

        PathManager.get_local_path(self._remote_uri, foo="foo")  # type: ignore
        f = PathManager.open(self._remote_uri, foo="foo")  # type: ignore
        f.close()
        PathManager.set_strict_kwargs_checking(True)

Notes:
        1. This function does not read the image and ground truth files.
           The results do not have the "image" and "sem_seg" fields.
    """

    # We match input images with ground truth based on their relative filepaths (without file
    # extensions) starting from 'image_root' and 'gt_root' respectively.
    def file2id(folder_path, file_path):
        # extract relative path starting from `folder_path`
        image_id = os.path.normpath(os.path.relpath(file_path, start=folder_path))
        # remove file extension
        image_id = os.path.splitext(image_id)[0]
        return image_id

    input_files = sorted(
        (os.path.join(image_root, f) for f in PathManager.ls(image_root) if f.endswith(image_ext)),
        key=lambda file_path: file2id(image_root, file_path),
    )
    gt_files = sorted(
        (os.path.join(gt_root, f) for f in PathManager.ls(gt_root) if f.endswith(gt_ext)),
        key=lambda file_path: file2id(gt_root, file_path),
    )

    assert len(gt_files) > 0, "No annotations found in {}.".format(gt_root)

    # Use the intersection, so that val2017_100 annotations can run smoothly with val2017 images
    if len(input_files) != len(gt_files):
        logger.warn(
            "Directory {} and {} has {} and {} files, respectively.".format(
                image_root, gt_root, len(input_files), len(gt_files)
            )
        )

# We match input images with ground truth based on their relative filepaths (without file
    # extensions) starting from 'image_root' and 'gt_root' respectively.
    def file2id(folder_path, file_path):
        # extract relative path starting from `folder_path`
        image_id = os.path.normpath(os.path.relpath(file_path, start=folder_path))
        # remove file extension
        image_id = os.path.splitext(image_id)[0]
        return image_id

    input_files = sorted(
        (os.path.join(image_root, f) for f in PathManager.ls(image_root) if f.endswith(image_ext)),
        key=lambda file_path: file2id(image_root, file_path),
    )
    gt_files = sorted(
        (os.path.join(gt_root, f) for f in PathManager.ls(gt_root) if f.endswith(gt_ext)),
        key=lambda file_path: file2id(gt_root, file_path),
    )

    assert len(gt_files) > 0, "No annotations found in {}.".format(gt_root)

    # Use the intersection, so that val2017_100 annotations can run smoothly with val2017 images
    if len(input_files) != len(gt_files):
        logger.warn(
            "Directory {} and {} has {} and {} files, respectively.".format(
                image_root, gt_root, len(input_files), len(gt_files)
            )
        )
        input_basenames = [os.path.basename(f)[: -len(image_ext)] for f in input_files]
        gt_basenames = [os.path.basename(f)[: -len(gt_ext)] for f in gt_files]
        intersect = list(set(input_basenames) & set(gt_basenames))
        # sort, otherwise each worker may obtain a list[dict] in different order

def get_all_checkpoint_files(self):
        """
        Returns:
            list: All available checkpoint files (.pth files) in target
                directory.
        """
        all_model_checkpoints = [
            os.path.join(self.save_dir, file)
            for file in PathManager.ls(self.save_dir)
            if PathManager.isfile(os.path.join(self.save_dir, file))
            and file.endswith(".pth")
        ]
        return all_model_checkpoints