Hi,

You can try this

public static final PortType OPTIONAL_PORT_TYPE = new PortType(BufferedDataTable.class, true);
/**
 * Constructor for the node model.
 */
protected MyLearnerNodeModel()
{
    // three incoming ports where port 1 and 3 are optional and one outgoing port is assumed
    super(createOPOs(3, 1, 3), createOPOs(1));
}
private static PortType[] createOPOs(final int nrDataPorts, final int... optionalPortsIds)
{
    PortType[] portTypes = new PortType[nrDataPorts];
    Arrays.fill(portTypes, BufferedDataTable.TYPE);        

    if (optionalPortsIds.length > 0) {
        for (int portId : optionalPortsIds) {
            if ((portId - 1) < nrDataPorts) {
                portTypes[portId - 1] = OPTIONAL_PORT_TYPE;
            }
        }
    }
    return portTypes;
}