src/main/java/org/jivesoftware/smack/util/collections/AbstractHashedMap.java
public Set<K> keySet() {
        if (keySet == null) {
            keySet = new KeySet<K, V>(this);
        }
        return keySet;
    }
public Set<K> keySet() {
        if (keySet == null) {
            keySet = new KeySet<K, V>(this);
        }
        return keySet;
    }
Gets the keySet view of the map. Changes made to the view affect this
map. To simply iterate through the keys, use {@link #mapIterator()}.

@return the keySet view