code: public TwoDHashMap<K2, K3, V> getAs2d(final K1 firstKey) {
  		final HashMap<K2, HashMap<K3, V>> innerMap1 = map.get(firstKey);
  		if( innerMap1 != null ) {
  			return new TwoDHashMap<K2, K3, V>(innerMap1);
  		} else {
  			return new TwoDHashMap<K2, K3, V>();
  		}
  		
  	}
docs: Fetch the outermost Hashmap as a TwoDHashMap.
  
  @param firstKey
  first key
  @return the the innermost hashmap