NetworkServer.SpawnWithClientAuthority Not found

I am trying to run this code.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Networking;


public class PlayerInput : NetworkBehaviour {
[Command]
  void CmdSpawnThirdCamera()
  {
    var camSpawn = (Third_Camera)Instantiate(third_Camera);

    NetworkServer.SpawnWithClientAuthority(camSpawn, connectionToClient);
  }
}

But i get this message from unity ? any ideas

NetworkServer' does not contain a definition for SpawnWithClientAuthority’

Fixed it… i was overriding the NetworkServer with my own script.