showGraph() {
    this.hierarchialGraph.nodes = [
      {
        id: '1',
        label: '1',
        position: 'x1'
      }
       ....
    ];

    this.hierarchialGraph.links = [
      {
        source: '1',
        target: '2',
        label: '1'
      }
       ....
    ];
  }

getNeighborNode(string) {
    for (const i of this.hierarchialGraph.links) {
      if (string === this.hierarchialGraph.links[i].source) {
        ...
      }
    }
 }