code: function addNodeToGraph(node){
  
      gNodesDisplayed.push(node);
      g.addNode(node._id, node);
  
  
      if (contains(childrenNodes, node._id)){
          var parentNode = getNodeFromId(nodesToBeLinked[node._id].from);
          if (contains(gNodesDisplayed, parentNode)){
              addLinkToParent(node._id, parentNode._id);
          }
      }
  }
docs: Add the node in param to the graph
  @param node