Old NPC Tutorial code doesn't work

I found this old tutorial with a example addon but the only problem is that it doesn’t work no more and I need help fixing this
original addon link: https://garrysmods.org/download/1821/shop-npc-examplezip



include('shared.lua') -- At this point the contents of shared.lua are ran on the client only.

function NPCShopMenu()

	-- Small derma panel just for the example.
	local pShop = vgui.Create('DFrame')
	pShop:SetSize(334, 63)
	pShop:SetPos(ScrW()*0.5, ScrH()*0.5)
	pShop:SetTitle('Rock & Gravel shop')

	-- We can also do anything else the client can do, like using the chat!
	chat.AddText(Color(255,255,128), "Merchant: ",Color(255,255,255), "Welcome to my shop, how can I help you?" )

usermessage.Hook("ShopNPCUsed", NPCShopMenu) --Hook to messages from the server so we know when to display the menu.


AddCSLuaFile( "cl_init.lua" ) -- This means the client will download these files
AddCSLuaFile( "shared.lua" )

include('shared.lua') -- At this point the contents of shared.lua are ran on the server only.

function ENT:Initialize( ) --This function is run when the entity is created so it's a good place to setup our entity.
	self:SetModel( "models/humans/group01/female_01.mdl" ) -- Sets the model of the NPC.
	self:SetHullType( HULL_HUMAN ) -- Sets the hull type, used for movement calculations amongst other things.
	self:SetHullSizeNormal( )
	self:SetSolid(  SOLID_BBOX ) -- This entity uses a solid bounding box for collisions.
	self:CapabilitiesAdd( CAP_ANIMATEDFACE | CAP_TURN_HEAD ) -- Adds what the NPC is allowed to do ( It cannot move in this case ).
	self:SetUseType( SIMPLE_USE ) -- Makes the ENT.Use hook only get called once at every use.
	self:SetMaxYawSpeed( 90 ) --Sets the angle by which an NPC can rotate at once.

function ENT:OnTakeDamage()
	return false -- This NPC won't take damage from anything.

function ENT:AcceptInput( Name, Activator, Caller )	

	if Name == "Use" and Caller:IsPlayer() then
		umsg.Start("ShopNPCUsed", Caller) -- Prepare the usermessage to that same player to open the menu on his side.
		umsg.End() -- We don't need any content in the usermessage so we're sending it empty now.


ENT.Base = "base_ai" -- This entity is based on "base_ai"
ENT.Type = "ai" -- What type of entity is it, in this case, it's an AI.
ENT.AutomaticFrameAdvance = true -- This entity will animate itself.
function ENT:SetAutomaticFrameAdvance( bUsingAnim ) -- This is called by the game to tell the entity if it should animate itself.
	self.AutomaticFrameAdvance = bUsingAnim

-- Since this file is ran by both the client and the server, both will share this information.