local function __TS__MapGroupBy(items, keySelector)
    local result = __TS__New(Map)
    local i = 0
    for ____, item in __TS__Iterator(items) do
        local key = keySelector(nil, item, i)
        if result:has(key) then
            local ____temp_0 = result:get(key)
            ____temp_0[#____temp_0 + 1] = item
        else
            result:set(key, {item})
        end
        i = i + 1
    end
    return result
end