getConnectedNodes(edgeId) {
    const nodeList = [];
    if (this.body.edges[edgeId] !== undefined) {
      const edge = this.body.edges[edgeId];
      if (edge.fromId !== undefined) {
        nodeList.push(edge.fromId);
      }
      if (edge.toId !== undefined) {
        nodeList.push(edge.toId);
      }
    }
    return nodeList;
  }
@param {Edge.id} edgeId
@returns {Array}