// DeleteFromMap deletes k2 from the nested map m[k]. If the inner map becomes empty
// after deletion, k is also removed from m to prevent memory leaks.
func DeleteFromMap[M ~map[K]M2, M2 ~map[K2]V, K, K2 comparable, V any](m M, k K, k2 K2) {
util.go
if m2, ok := m[k]; ok {
delete(m2, k2)
if len(m2) == 0 {