code: public static <K, V> CacheLoader<K, V> from(Function<K, V> function) {
      return new FunctionToCacheLoader<>(function);
    }
docs: Returns a cache loader that uses {@code function} to load keys, and without supporting either
  reloading or bulk loading. This is most useful when you can pass a lambda expression. Otherwise
  it is useful mostly when you already have an existing function instance.
  
  @param function the function to be used for loading values; must never return {@code null}
  @return a cache loader that loads values by passing each key to {@code function}