Rbx Lua Classes can't grab models?

The error is that the values assigned in the new method are nil to other methods of the class. How can I have the values not be nil when a method requests for them? As when I spawn a NPC and ask for the CFrame, it states self is nil.

local NPC= {}
NPC._index = NPC

function NPC.new(model)
    local entity = setmetatable({}, NPC)
    for index, value in pairs (NPC) do
        entity[index] = value
    end
    entity.Self = model
    entity.Settings = model:WaitForChild("Configurations")
    entity["Mind"] = model.Mind
    return entity
end

function NPC:GetCFrame()
    local humanoidRootPart = self.Self:FindFirstChild("humanoidRootPart")
    if humanoidRootPart and humanoidRootPart:IsA("BasePart") then
        print(humanoidRootPart.CFrame)
        return humanoidRootPart.CFrame
    else
        return CFrame.new()
    end
end

function NPC:Initialize()
    NPC:GetCFrame()
end

return NPC