Attempt To Call Missing Method IsADescendantOf()

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#1 
if not self["Model"]:IsADescendantOf(Client:WaitForChild("Backpack")) then 
		return error(tonumber(-1))
	else 
		self["Model"].Activated:Connect(function() Events.SwordEvent:FireServer() end)
	end
	

function SM_Client.Configure(Pack, Damage, Model)
	local Loaded, Errored = pcall(function()
		local self = setmetatable({}, SM_Client)
		self["Pack"] = Pack
		self["Damage"] = Damage
		self["Model"] = Model
	end) if not Loaded then return error(tonumber(-1)) else return print("Test: Success") end
#2

Try defining self.Model inside the table in setmetatable. If that doesn’t work, make sure you’re passing a model.