Degree of a monomial containing noncommutative variable

[atbug]

I am not sure whether there is a standard definition of degree for monomial containing non-commutative variables, but I think the following behavior is counter-intuitive:

julia> using DynamicPolynomials

julia> @ncpolyvar x y z
(x, y, z)

julia> degree(x*y*x, x)
1

Maybe the degree function can be modified as something like

function degree(m::AbstractMonomial, v::AbstractVariable)
    indices = findall(isequal(v), variables(m))
    if isempty(indices)
        return 0
    else
        return sum(exponents(m)[indices])
    end
end

Any comments?