How to use the dbutils.describe_file function in DBUtils

def processFile(file_id):
        components = dbutils.describe_file(db, file_id).split("/")
        directories, files = root_directories, root_files
        for directory_name in components[:-1]:
            directories, files = directories.setdefault(directory_name, ({}, {}))
        files[components[-1]] = file_id

Returns false if the creating a comment at the specified location is not
        supported, typically because the commit is not being reviewed in the
        review.
        """

        assert first_line > 0
        assert last_line >= first_line

        if not review.containsCommit(self.db, commit, True):
            return False

        self.review = review
        self.rebases = review.getReviewRebases(self.db)
        self.initial_commit = commit
        self.addressed_by = []
        self.file_path = dbutils.describe_file(self.db, file_id)
        self.file_id = file_id
        self.location = Location(first_line, last_line)
        self.active = True

        file_entry = commit.getFileEntry(self.file_path)

        if file_entry is None:
            # File doesn't exist (in the given commit.)
            return False

        diff_file = diff.File(new_sha1=file_entry.sha1,
                              new_mode=file_entry.mode,
                              repository=review.repository)
        diff_file.loadNewLines()

        if last_line > diff_file.newCount():

def renderFiles(db, to_user, review, title, files_lines, commits=None, relevant_only=False, relevant_files=None, showcommit_link=False):
    result = ""
    if files_lines:
        files = []

        for file_id, delete_count, insert_count in files_lines:
            if not relevant_only or file_id in relevant_files:
                files.append((dbutils.describe_file(db, file_id), delete_count, insert_count))

        if files:
            paths = []
            deleted = []
            inserted = []

            for path, delete_count, insert_count in sorted(files):
                paths.append(path)
                deleted.append(delete_count)
                inserted.append(insert_count)

            paths = diff.File.eliminateCommonPrefixes(paths, text=True)

            len_paths = max(map(len, paths))
            len_deleted = max(map(len, map(str, deleted)))
            len_inserted = max(map(len, map(str, inserted)))

def moduleFromFile(file_id):
            filename = dbutils.describe_file(db, file_id)
            return getModuleFromFile(repository, filename) or filename

def formatFiles(files):
        paths = sorted([dbutils.describe_file(db, file_id) for file_id in files])
        if granularity == "file":
            return diff.File.eliminateCommonPrefixes(paths)
        else:
            modules = set()
            files = []
            for path in paths:
                match = re_module.match(path)
                if match: modules.add(match.group(1))
                else: files.append(path)
            return sorted(modules) + diff.File.eliminateCommonPrefixes(files)

def renderCodeCommentChain(db, target, user, review, chain, context_lines=3, compact=False, tabify=False, original=False, changeset=None, linkify=False):
    repository = review.repository

    old_sha1 = None
    new_sha1 = None

    old = 1
    new = 2

    cursor = db.cursor()

    file_id = chain.file_id
    file_path = dbutils.describe_file(db, file_id)

    if (chain.state != "addressed" or original) and chain.first_commit == chain.last_commit:
        sha1 = chain.first_commit.getFileSHA1(file_path)

        cursor.execute("SELECT first_line, last_line FROM commentchainlines WHERE chain=%s AND sha1=%s", (chain.id, sha1))
        first_line, last_line = cursor.fetchone()

        file = diff.File(file_id, file_path, sha1, sha1, review.repository, chunks=[])
        file.loadNewLines(True)

        start = max(1, first_line - context_lines)
        end = min(file.newCount(), last_line + context_lines)
        count = end + 1 - start

        lines = file.newLines(True)
        lines = [diff.Line(diff.Line.CONTEXT, start + index, lines[start + index - 1], start + index, lines[start + index - 1]) for index in range(count)]

"original": commit == parent,
                                              "current": commit == child }
                                            for commit in annotator.commits],
                                   files=files)
        except LineAnnotator.NotSupported:
            blame = gitutils.Blame(parent, child)

            paths = {}

            for file in files:
                file_id = file["id"]

                path = paths.get(file_id)

                if not path:
                    path = paths[file_id] = dbutils.describe_file(db, file_id)

                for block in file["blocks"]:
                    block["lines"] = blame.blame(db, path, block["first"], block["last"])

            return OperationResult(commits=blame.commits, files=files)

def renderFiles(title, cursor):
        files = []

        for file_id, delete_count, insert_count in cursor.fetchall():
            files.append((dbutils.describe_file(db, file_id), delete_count, insert_count))

        paths = []
        deleted = []
        inserted = []

        for path, delete_count, insert_count in sorted(files):
            paths.append(path)
            deleted.append(delete_count)
            inserted.append(insert_count)

        if paths:
            diff.File.eliminateCommonPrefixes(paths)

            row = table.tr("line")
            row.td("heading").text(title)