Immutable bidirectional map in Julia.
In most cases, you probably don't want to use this package but rather
] add https://github.com/rikhuijzer/BidirectionalMaps.jl
julia> using BidirectionalMaps
julia> U = ["A", "D", "B"];
julia> V = ["F", "G", "B"];
julia> b = ImmutableBimap{String,String}(U, V);
julia> b.left["A"]
"F"
julia> b.right["F"]
"A"