code: def get_uids(self, filename=None):
          
          self._update()
  
          if filename:
              if filename not in self._reminders:
                  return []
              return self._reminders[filename].keys()
          return [uid for uids in self._reminders.values() for uid in uids]
docs: UIDs of all reminders in the file excluding included files
          If a filename is specified, only it's UIDs are return, otherwise all.
  
          filename -- the remind file