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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _populate_list(self, value):
 """ Populate the current multi-column list with the contents of the selected directory. :param value: The new value to use. """

        # Nothing to do if the value is rubbish.
        if value is None:
            return

        # Stop any recursion - no more returns from here to end of fn please!
        if self._in_update:
            return
        self._in_update = True

        # We need to update the tree view.
        self._root = os.path.abspath(value if os.path.isdir(value) else os.path.dirname(value))

        # The absolute expansion of "/" or "\" is the root of the disk, so is a cross-platform
        # way of spotting when to insert ".." or not.
        tree_view = []
        if len(self._root) > len(os.path.abspath(os.sep)):
            tree_view.append((["|-+ .."], os.path.abspath(os.path.join(self._root, ".."))))

        tree_dirs = []
        tree_files = []
        try:
            files = os.listdir(self._root)
        except OSError:
            # Can fail on Windows due to access permissions
            files = []
        for my_file in files:
            full_path = os.path.join(self._root, my_file)
            try:
                details = os.lstat(full_path)
            except OSError:
                # Can happen on Windows due to access permissions
                details = namedtuple("stat_type", "st_size st_mtime")
                details.st_size = 0
                details.st_mtime = 0
            name = "|-- {}".format(my_file)
            tree = tree_files
            if os.path.isdir(full_path):
                tree = tree_dirs
                if os.path.islink(full_path):
                    # Show links separately for directories
                    real_path = os.path.realpath(full_path)
                    name = "|-+ {} -> {}".format(my_file, real_path)
                else:
                    name = "|-+ {}".format(my_file)
            elif self._file_filter and not self._file_filter.match(my_file):
                # Skip files that don't match the filter (if present)
                continue
            elif os.path.islink(full_path):
                # Check if link target exists and if it does, show statistics of the
                # linked file, otherwise just display the link
                try:
                    real_path = os.path.realpath(full_path)
                except OSError:
                    # Can fail on Linux prof file system.
                    real_path = None
                if real_path and os.path.exists(real_path):
                    details = os.stat(real_path)
                    name = "|-- {} -> {}".format(my_file, real_path)
                else:
                    # Both broken directory and file links fall to this case.
                    # Actually using the files will cause a FileNotFound exception
                    name = "|-- {} -> {}".format(my_file, real_path)

            # Normalize names for MacOS and then add to the list.
            tree.append(([unicodedata.normalize("NFC", name),
                          readable_mem(details.st_size),
                          readable_timestamp(details.st_mtime)], full_path))

        tree_view.extend(sorted(tree_dirs))
        tree_view.extend(sorted(tree_files))

        self.options = tree_view
        self._titles[0] = self._root

        # We're out of the function - unset recursion flag.
        self._in_update = False