code: def srt_formatter(subtitles, padding_before=0, padding_after=0):
      
      sub_rip_file = pysrt.SubRipFile()
      for i, ((start, end), text) in enumerate(subtitles, start=1):
          item = pysrt.SubRipItem()
          item.index = i
          item.text = six.text_type(text)
          item.start.seconds = max(0, start - padding_before)
          item.end.seconds = end + padding_after
          sub_rip_file.append(item)
      return '\n'.join(six.text_type(item) for item in sub_rip_file)
docs: Serialize a list of subtitles according to the SRT format, with optional time padding.