Auxiliary functions

Function sets a label for a randomization procedure. An example:

julia> w = [1, 2, 3, 4]
4-element Vector{Int64}:
 1
 2
 3
 4

julia> dlud = DLUD(w, 2)
DLUD(2): restricted randomization procedure, targeting 1:2:3:4 allocation in 4-arm trial.

julia> label(dlud)
"DLUD(2)"