DRAのsubmission idからメタデータのファイルリストをftpで取得する関数

def create_xml_list(self, ftp_server, archive_path, submission):
        ftp = FTP(ftp_server)
        ftp.login()
        num = int(submission[3:])
        n = "DRA" + str(int(num/1000)).zfill(3)
        xml_file_path = "/".join([archive_path, n, submission])
        ftp.cwd(xml_file_path)
        xml_list = []
        try:
            xml_list = ftp.mlsd()
        except ftplib.error_perm as erm:
            if str(erm) == "550 No files found":
                print("No files in this directory")
            else:
                raise

        return xml_list