How do I make my script properly find the players mouse? player:GetMouse() [closed]

player = script.Parent.Parent.Parent
mouse = player:GetMouse()
invBox = game.StarterGui.ScreenGui.Frame
local open = false

function inv(key)
    key = key:lower()

    if key == "p" then
        if open then
        player.PlayerGui.ScreenGui.Frame.Visible = false -- You can change "Frame" or "ScreenGui" to your Gui's name(s)
        open = true 
        open = false
        return 
        end
        if not open then
        player.PlayerGui.ScreenGui.Frame.Visible = true -- You can change "Frame" or "ScreenGui" to your Gui's name(s)
        open = true 
        end
    end

end

mouse.KeyDown:connect(inv)

If I were to put the script into PlayerScripts then it would work just fine

if I make player = script.Parent.Parent