code: public static final <K, V> Map<K, V> map(K key, V value) {
          Map<K, V> map = new HashMap<>();
          map.put(key, value);
          return map;
      }
docs: Reduces overhead compared to the far more advanced {@link #map(Object...)}.
  
  @param key A single key
  @param <K> type of the key
  @param value A single value
  @param <V> type of the value
  @return A Modifiable Map with a single entry