@staticmethod<EOL><INDENT>def add_unique_postfix(fn):<DEDENT>
fn = p_compat.str(fn)<EOL>if not os.path.exists(fn):<EOL><INDENT>return fn<EOL><DEDENT>path, name = os.path.split(fn)<EOL>name, ext = os.path.splitext(name)<EOL>make_fn = lambda i: os.path.join(path, '<STR_LIT>' % (name, i, ext))<EOL>for i in p_compat.xrange(<NUM_LIT:2>, sys.maxsize):        <EOL><INDENT>uni_fn = make_fn(i)<EOL>if not os.path.exists(uni_fn):            <EOL><INDENT>return uni_fn<EOL><DEDENT><DEDENT>return None<EOL>
@param fn: File name
@return:  Return an unique postfix for the file name