code: @Override
  	public <NK, NV> FMap<NK, NV> map(BiFunction<? super K, ? super V, Product2<? extends NK, ? extends NV>> f) {
  		HashFMap<NK, NV> ret = new HashFMap<>(new HashMap<>(this.size()));
  		for (java.util.Map.Entry<K, V> entry : entrySet()) {
  			Product2<? extends NK,? extends NV> t = f.apply(entry.getKey(), entry.getValue());
  			ret.put(t.get1(), t.get2());
  		}
  		return ret;
  	}
docs: ========== NEW F METHODS =========