docs: @Override
  	public void clear() {
  		if (this.nNorthWest != null) {
  			final N child = this.nNorthWest;
  			setFirstChild(null);
  			child.clear();
  		}
  		if (this.nNorthEast != null) {
  			final N child = this.nNorthEast;
  			setSecondChild(null);
  			child.clear();
  		}
  		if (this.nSouthWest != null) {
  			final N child = this.nSouthWest;
  			setThirdChild(null);
  			child.clear();
  		}
  		if (this.nSouthEast != null) {
  			final N child = this.nSouthEast;
  			setFourthChild(null);
  			child.clear();
  		}
  		removeAllUserData();
  	}