code: @Override
  	public void createMinYFunction() {
  		createFunction(MIN_Y_FUNCTION, new GeometryFunction() {
  			@Override
  			public Object execute(GeoPackageGeometryData data) {
  				Object value = null;
  				GeometryEnvelope envelope = getEnvelope(data);
  				if (envelope != null) {
  					value = envelope.getMinY();
  				}
  				return value;
  			}
  		});
  	}
docs: {@inheritDoc}