std::unordered_map - Header only reverse map from forward map using lambda

reverse_map_snippit.hpp

#pragma once
#include <unordered_map>
#include <utility>

enum class test_e : int64_t
{
    one,
    two,
    three
};

// forward map
static const std::unordered_map<string, test_e> testForwardMap = {
    {"one", test_e::one},
    {"two", test_e::two},
    {"three", test_e::three}
};  

// reverse map
static const std::unordered_map<test_e, string> testReverseMap([]()->std::unordered_map<test_e,string>{
    std::unordered_map<test_e, string> res;
    for (auto &i : testForwardMap)
        res.emplace(i.second, i.first);
    return std::move(res);
}());