Bounds are not contracting using 'ReversePropagation.jl'

General Usage
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1

Hello,

I am trying to run an example code given for illustrating the working of ReversePropagation.jl. But it is neither working in Pluto.jl notebook nor in VSCode. Could anyone please check if I am making any mistakes? The code is:

using Symbolics
using IntervalArithmetic
using ReversePropagation

vars = @variables x, y
	    
ex = x^2 + y^2
    
C = forward_backward_contractor(ex, vars)  # construct the contractor

constraint = Interval(0, 1)

X = IntervalBox(Interval(-10,10), 2)

C(X, constraint)

Error-1:

C = forward_backward_contractor(ex, vars)  # construct the contractor
ERROR: MethodError: rev(::typeof(+), ::Num, ::Num, ::Num) is ambiguous.

Error-2:

C(X, constraint)
ERROR: UndefVarError: `C` not defined