code: def _format_snapshots(snapshots: List[icontract._Snapshot], prefix: Optional[str] = None) -> List[str]:
      
      if not snapshots:
          return []
  
      result = []  # type: List[str]
  
      if prefix is not None:
          result.append(":{} OLD:".format(prefix))
      else:
          result.append(":OLD:")
  
      for snapshot in snapshots:
          text = _capture_as_text(capture=snapshot.capture)
          result.append("    * :code:`.{}` = :code:`{}`".format(snapshot.name, text))
  
      return result
docs: Format snapshots as reST.
  
      :param snapshots: snapshots defined to capture the argument values of a function before the invocation
      :param prefix: prefix to be prepended to ``:OLD:`` directive
      :return: list of lines describing the snapshots