code: function _addVertexGroupBubble(node, d) {
    var group;
  
    if(d.vertexGroup) {
      group = node.append('g');
      group.attr('class', 'group-bubble');
      group.append('use').attr('xlink:href', '#group-bubble');
      translateIfIE(group.append('text')
          .text(_trimText(d.get('vertexGroup.groupMembers.length'), 2)), 0, 4);
  
      translateIfIE(group, 38, 15);
    }
  }
docs: Add vertex group bubble to a vertex node
  @param node {SVG DOM element} Vertex node
  @param d {VertexDataNode}