code: public static <K, V> Map<K, V> select_keys_pred(Set<K> filter, Map<K, V> all) {
          Map<K, V> filterMap = new HashMap<>();
  
          for (Entry<K, V> entry : all.entrySet()) {
              if (!filter.contains(entry.getKey())) {
                  filterMap.put(entry.getKey(), entry.getValue());
              }
          }
  
          return filterMap;
      }
docs: filter the map