"TweenPosition is not a valid member of UDim2"?

This is a script for a basic button press animation script (I guess?)

local down = false

local lastpos = script.Parent.Position

script.Parent.MouseButton1Down:connect(function()
	if down == false then
			down = true
			script.Parent.Frame.Position = UDim2.new(0,0,0,1)
			script.Parent.Position:TweenPosition(UDim2.new(script.Parent.Position + UDim2.new(0,0,0,4.5)), Enum.EasingStyle.Quad)
			script.Parent.Text = "Play"
			
			script.Parent.MouseButton1Up:connect(function()
			script.Parent.Frame.Position = UDim2.new(0,0,0,5)
			script.Parent.Position = lastpos
			script.Parent.Text = "Play"
			down = false
			end)
	end
end)

The output: 21:39:44.953 - TweenPosition is not a valid member of UDim2 21:39:44.953 - Stack Begin 21:39:44.954 - Script 'Players.Player1.PlayerGui.ScreenGui.Frame.TextButton.LocalScript', Line 9 21:39:44.954 - Stack End

Why is TweenPosition not a valid member of UDim2?

script.Parent:TweenPosition(UDim2.new(script.Parent.Position + UDim2.new(0,0,0,4.5)), Enum.EasingStyle.Quad)

You don't need to use position as you're tweening off the current position.

local down = false

local lastpos = script.Parent

script.Parent.MouseButton1Down:connect(function()
    if down == false then
            down = true
            script.Parent.Frame.Position = UDim2.new(0,0,0,1)
            script.Parent.Position:TweenPosition(UDim2.new(0,0,0,4.5), 'In', 'Quad', .5)
            script.Parent.Text = "Play"
else
    if down == true then
            script.Parent.MouseButton1Up:connect(function()
            script.Parent:TweenPosition(UDim2.new(0,0,0,5), 'Out', 'Quad', .5)
            script.Parent.Position = lastpos
            script.Parent.Text = "Play"
            down = false
            end)
	end
end)

This should work I hope you had a lot of mistakes like else. [Edited]