code: public Keys<K> keys () {
  		if (keys == null)
  			keys = new Keys(this);
  		else
  			keys.reset();
  		return keys;
  	}
docs: Returns an iterator for the keys in the map. Remove is supported. Note that the same iterator instance is returned each
  time this method is called. Use the {@link Entries} constructor for nested or multithreaded iteration.