docs: def WriteClientSnapshotHistory(self, clients):
      """Writes the full history for a particular client."""
      if clients[0].client_id not in self.metadatas:
        raise db.UnknownClientError(clients[0].client_id)
  
      for client in clients:
        startup_info = client.startup_info
        client.startup_info = None
  
        snapshots = self.clients.setdefault(client.client_id, {})
        snapshots[client.timestamp] = client.SerializeToString()
  
        startup_infos = self.startup_history.setdefault(client.client_id, {})
        startup_infos[client.timestamp] = startup_info.SerializeToString()
  
        client.startup_info = startup_info