code: def _expand_argument(self, arg):
          
          if isinstance(arg, R): return [arg.str]
          scope = self._scope or self._exports
          arg = arg % scope
          arg = os.path.expanduser(arg)
          res = glob.glob(self._expand_path(arg))
          if not res: return [arg]
          if self._cwd != "/":
              for idx in xrange(0, len(res)):
                  if res[idx].startswith(self._cwd + "/"):
                      res[idx] = "./" + res[idx][len(self._cwd + "/"):]
          return res
docs: Performs argument glob expansion on an argument string.
          Returns a list of strings.