code: function groupNode(node) {
    node.parent = node.parent || '';
  
    if(groupedDelta[node.id] === undefined) {
      groupedDelta[node.id] = {
        id: node.id,
        directory: node.directory,
        actions: {}
      };
    } else if(groupedDelta[node.id].directory === undefined && node.directory !== undefined) {
      // Since balloon v2.1.0 action: directory is undefined for delete actions
      groupedDelta[node.id].directory = node.directory;
    }
  
    var groupedNode = groupedDelta[node.id];
  
    if(node.deleted !==false && node.deleted !== undefined) {
      //in rare cases node.deleted might be a timestamp
      groupedNode.actions.delete = node;
    } else {
      groupedNode.actions.create = node;
      groupedNode.parent = node.parent;
      if(node.directory === false) {
        groupedNode.version = node.version;
        groupedNode.hash = node.hash;
        groupedNode.size = node.size;
      }
    }
  }
docs: groups a single node
  
  @param {Object} node - node action from remote delta
  @returns {void} - no return value