code: def _filename(self, ifo, description, extension, segment):
          
          if extension.startswith('.'):
              extension = extension[1:]
  
          # Follow the frame convention of using integer filenames,
          # but stretching to cover partially covered seconds.
          start = int(segment[0])
          end = int(math.ceil(segment[1]))
          duration = str(end-start)
          start = str(start)
  
          return "%s-%s-%s-%s.%s" % (ifo, description.upper(), start,
                                     duration, extension)
docs: Construct the standard output filename. Should only be used internally
          of the File class.