denominator for polynomials

[SoongNoonien]

I was again playing around with the universal polynomial rings and wondered why there is no denominator function for them. But then I noticed that with plain AbstractAlgebra there is not even a denominator function for univariate or multivariate polynomials:

julia> using AbstractAlgebra

julia> pkgversion(AbstractAlgebra)
v"0.41.9"

julia> R,(x,y)=QQ[:x,:y]
(Multivariate polynomial ring in 2 variables over rationals, AbstractAlgebra.Generic.MPoly{Rational{BigInt}}[x, y])

julia> denominator(1//2*x+1//3*x^2)
ERROR: MethodError: no method matching denominator(::AbstractAlgebra.Generic.MPoly{Rational{BigInt}})

Closest candidates are:
  denominator(::AbstractAlgebra.Generic.RationalFunctionFieldElem, ::Bool)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/RationalFunctionField.jl:90
  denominator(::AbstractAlgebra.Generic.RationalFunctionFieldElem)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/RationalFunctionField.jl:90
  denominator(::AbstractAlgebra.Generic.TotFrac, ::Bool)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/TotalFraction.jl:73
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[3]:1

julia> R,x=QQ[:x]
(Univariate polynomial ring in x over rationals, x)

julia> denominator(1//2*x+1//3*x^2)
ERROR: MethodError: no method matching denominator(::AbstractAlgebra.Generic.Poly{Rational{BigInt}})

Closest candidates are:
  denominator(::AbstractAlgebra.Generic.RationalFunctionFieldElem, ::Bool)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/RationalFunctionField.jl:90
  denominator(::AbstractAlgebra.Generic.RationalFunctionFieldElem)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/RationalFunctionField.jl:90
  denominator(::AbstractAlgebra.Generic.TotFrac, ::Bool)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/TotalFraction.jl:73
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[6]:1

julia> R=universal_polynomial_ring(QQ)
Universal Polynomial Ring over Rationals

julia> x=gen(R,:x)
x

julia> denominator(1//2*x+1//3*x^2)
ERROR: MethodError: no method matching denominator(::AbstractAlgebra.Generic.UnivPoly{Rational{BigInt}, AbstractAlgebra.Generic.MPoly{Rational{BigInt}}})

Closest candidates are:
  denominator(::AbstractAlgebra.Generic.RationalFunctionFieldElem, ::Bool)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/RationalFunctionField.jl:90
  denominator(::AbstractAlgebra.Generic.RationalFunctionFieldElem)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/RationalFunctionField.jl:90
  denominator(::AbstractAlgebra.Generic.TotFrac, ::Bool)
   @ AbstractAlgebra ~/.julia/packages/AbstractAlgebra/EYoda/src/generic/TotalFraction.jl:73
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[10]:1

julia> 

In all of these cases I would expect a value of 6.