code: function drawNodeContext(nodeId, nbHops){
      clearGraph();
  
      var node = searchNodeInTree(gTree, nodeId);
      if (!contains(gNodesDisplayed, node.node)){
          addNodeToGraph(node.node);
          addRelToGraph(node.node);
      }
  
      if (node.childNodes){
          var lastNode;
          var nodesWithChildren = [node];
          for (var i = 0; i < nbHops; ++i){
              var currentNode = nodesWithChildren[i];
              if (currentNode){
                  var childNodes = currentNode.childNodes;
                  for (var j = 0; j < childNodes.length; ++j){
                      var currChild = childNodes[j];
                      if (!contains(gNodesDisplayed, currChild.node)){
                          addNodeToGraph(currChild.node);
                      }
                      if (contains (gNodesWithRel, currChild.node)){
                          addRelToGraph(currChild.node);
                          nodesWithChildren.push(currChild);
                      }
                  }
                  lastNode = currentNode;
              } else {
                  nbHops = (nodesWithChildren.length > nbHops ? nbHops : nodesWithChildren.length);
              }
          }
      }
  
      if (isPaused){
          renderer.rerender();
      }
  }
docs: Deletes the current graph and draws the node and its children (depth of nbHops)
  @param nodeId
  @param nbHops