prices = Dict(
    "milk" => 1,
    "eggs" => 2,
    "cheese" => 3.5,
    "bread" => 0.9,
    "chocolate" => 2.2,
    "flour" => 0.5,
    "tomatoes" => 1.5
)

stock = Dict(
    "milk" => 10,
    "eggs" => 20,
    "cheese" => 35,
    "bread" => 20,
    "chocolate" => 22,
    "flour" => 15,
    "tomatoes" => 15
)

mutable struct Store
    stock::Dict
    prices::Dict
    funds::Float64
end

store = Store(prices, stock, 100)
println(store.stock["milk"])
println(store.prices["tomatoes"])
println(sum(values(store.prices)))

map(sum, collect(values(prices)))
map(sum, collect(values(prices)))
println(keys(store.prices))