Stop is not a valid member of Animation "Animation" Same goes for Play???

This script does so that a anim plays when your walking sideways but the problem is that this happends:

Stop is not a valid member of Animation "Animation" Play is not a valid member of Animation "Animation" Why??

Heres the localscript:

local plr = game.Players.LocalPlayer
local char = plr.Character
local hum = char:WaitForChild("Humanoid")
local UserInputService = game:GetService("UserInputService")

local leftWalk = Instance.new("Animation")
leftWalk.AnimationId = "rbxassetid://6046738829"

local rightWalk = Instance.new("Animation")
rightWalk.AnimationId = "rbxassetid://6046765944"

hum:LoadAnimation(leftWalk)
hum:LoadAnimation(rightWalk)

UserInputService.InputBegan:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.D then
        print("Going Right")
        rightWalk:Play()
    elseif input.KeyCode == Enum.KeyCode.A then
        print("Going Left")
        leftWalk:Play()
    end
end)

UserInputService.InputEnded:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.D then
        print("Animation Stop")
        rightWalk:Stop()
    elseif input.KeyCode == Enum.KeyCode.A then
        print("Animation Stop")
        leftWalk:Stop()
    end
end)