anchor.diff:  
                       function handle_click(event,group_id) {
                            var target = event.target;
  -
                            if (group_id == "nodes"){
                                clear("edges");
                            }
  
positive.code:                       vis.updateData([target]);
                    };
                }
                function getDataFields(group_id) {
                    var schema = vis.dataSchema();
                    var nodeFields = schema.nodes;
                    var edgeFields = schema.edges;
  
                    if (group_id == "nodes") {
                        return nodeFields;
                    }
                    if (group_id == "edges") {
                        return edgeFields;
                    }
  
                }
  
  
negative.code:                 // callback when Cytoscape Web has finished drawing
                  vis.ready(function() {
  
                      //get all data fields of nodes and edges
                      nodesDataSchema = getDataSchema("nodes");
                      edgesDataSchema = getDataSchema("edges");
  
                      var comment_field = { name: "Comment", type: "string", defValue: null };
                      //Add new comment field to nodes and edges if not existed:
                      if (checkDataField("nodes","Comment") == undefined) {
                          vis.addDataField("nodes",comment_field);
                          nodesDataSchema = getDataSchema("nodes");
                      }
                      if (checkDataField("edges","Comment") == undefined) {
                          vis.addDataField("edges",comment_field);
                          edgesDataSchema = getDataSchema("edges");
                      }
  
                      // add a listener for when nodes and edges are clicked
                      vis.addListener("click", "nodes", function(event) {
                          //Add new comment field to nodes and edges if not existed:
                          handle_click(event,"nodes");
                      })
                      .addListener("click", "edges", function(event) {
  