MathematicalSystems.jl with input constraint only

Dear all,

I would like to know if there is a mathematical system structure with only input constraints, for instance:

julia> using LazySets
julia> using MathematicalSystems
julia> A = [1 1; 0 0.9]
julia> B = [1; 0.5]
julia> U = Hyperrectangle(low=[-1], high=[1])
julia> system = @system x⁺ = A*x + B*u u∈U

It provides me an issue:

julia> system = @system x⁺ = A*x + B*u u∈U
ERROR: ArgumentError: the entry (:A, :B, :U) does not match a `MathematicalSystems.jl` structure
 [1] top-level scope
   @ REPL[6]:1

Is there a workaround?

Warmest regards