def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def GetLogs(region, stream_name, group_name, token=None):
  """Fetches the JSON formatted log stream starting at the token."""
  get_cmd = util.AWS_PREFIX + [
      '--region', region,
      'logs', 'get-log-events',
      '--start-from-head',
      '--log-group-name', group_name,
      '--log-stream-name', stream_name,
  ]
  if token:
    get_cmd.extend(['--next-token', token])
  stdout, _, _ = vm_util.IssueCommand(get_cmd)
  return json.loads(stdout)