     // The following offsets assume the strokeWidth == 1.
          {
            key: 1,
            geo: 'F1 M0 0 L20 0 20 20 0 20z',
            ports: [
              { id: 'U6', spot: '0.5 0 0 0.5' },
              { id: 'U2', spot: '0.5 1 0 -0.5' }
            ]
          },
          {
            key: 3,
            angle: 90,
            geo: 'F1 M0 0 L20 0 20 20 0 20z',
            ports: [
              { id: 'U6', spot: '0.5 0 0 0.5' },
              { id: 'U2', spot: '0.5 1 0 -0.5' }
         