Does not implement interface member 'IPunObservable.OnPhotonSerializeView'

Hello, I'm new to PUN and I got this error two scripts: SmoothSyncMovement and CullingHandler, saying that they dont implement interface member 'IPunObservable.OnPhotonSerializeView'. I use Visual Studio, and tried to implement the OnPhotonSerializeView, it does create it but there is already another one present in the script. I have no clue how to solve the error, it would be great if someone could help.