code: public boolean isVertexIgnored(Object vertex) {
      return super.isVertexIgnored(vertex) || graph.isSwimlane(vertex) || graph.getModel().getGeometry(vertex).isRelative() || graph.getConnections(vertex).length == 0;
    }
docs: Returns a boolean indicating if the given <em>mxCell</em> should be ignored as a vertex. This returns true if the cell has no connections.
  
  @param vertex
  Object that represents the vertex to be tested.
  @return Returns true if the vertex should be ignored.