How to use the pysubs2.common.PY3 function in pysubs2

if args.output_format is None:
                        outpath = path
                        output_format = subs.format
                    else:
                        ext = get_file_extension(args.output_format)
                        outpath = change_ext(path, ext)
                        output_format = args.output_format

                    if args.output_dir is not None:
                        _, filename = op.split(outpath)
                        outpath = op.join(args.output_dir, filename)

                    with open(outpath, "w", encoding=args.output_enc) as outfile:
                        subs.to_file(outfile, output_format, args.fps)
        else:
            if PY3:
                infile = io.TextIOWrapper(sys.stdin.buffer, args.input_enc)
                outfile = io.TextIOWrapper(sys.stdout.buffer, args.output_enc)
            else:
                infile = io.TextIOWrapper(sys.stdin, args.input_enc)
                outfile = io.TextIOWrapper(sys.stdout, args.output_enc)

            subs = SSAFile.from_file(infile, args.input_format, args.fps)
            self.process(subs, args)
            output_format = args.output_format or subs.format
            subs.to_file(outfile, output_format, args.fps)

        return (0 if errors == 0 else 1)

def __repr__(self):
        s = "".format(
                self=self, start=ms_to_str(self.start), end=ms_to_str(self.end))
        if not PY3: s = s.encode("utf-8")
        return s

def __repr__(self):
        s = "

def to_file(cls, subs, fp, format_, **kwargs):
        data = {
            "info": dict(**subs.info),
            "styles": {name: sty.as_dict() for name, sty in subs.styles.items()},
            "events": [ev.as_dict() for ev in subs.events]
        }

        if PY3:
            json.dump(data, fp)
        else:
            text = json.dumps(data, fp)
            fp.write(unicode(text))

def __repr__(self):
        if self.events:
            max_time = max(ev.end for ev in self)
            s = "" % \
                    (len(self), len(self.styles), ms_to_str(max_time))
        else:
            s = "" % len(self.styles)

        if not PY3: s = s.encode("utf-8")
        return s