4} lo.Filter(numbers, func(x int, _ int) bool { return x%2 == 0 }) // []int{2, 4} lo.Map(numbers, func(x int, _ int) int { return x * 2 }) // []int{2, 4, 6, 8} mapA := map[string]int{"foo": 10} mapB := map[string]int{"bar": 20} lo.FindKey(mapA, 10) // foo, true lo.Assign(mapA, mapB) // map[string]int{"foo": 10, "bar": 20}