saveNodePositions(positions) {

    const nodeData = this.getNodeData();

    for (let id in positions) {

      nodeData[id] = nodeData[id] || {};
      nodeData[id].x = positions[id].x;
      nodeData[id].y = positions[id].y;

    }

    this.saveNodeData(nodeData);

  }
Saves a node's position to the store

@param {Object} positions