Package or Function to find and access keys in a nested dicts

New to Julia
2

Are you sure your example is completely free of typos? It works fine for me:

julia> hydrogen_dict = Dict("TRANSPORT" => Dict("viscosity" => Dict("dilute" => Dict("molar_mass" => 2.016))))
Dict{String, Dict{String, Dict{String, Dict{String, Float64}}}} with 1 entry:
  "TRANSPORT" => Dict("viscosity"=>Dict("dilute"=>Dict("molar_mass"=>2.016)))

julia> retrieve(hydrogen_dict, "molar_mass")
2.016