getSpanningTreeNeighbours(vertexId = null) {
    let neighbours = Array();

    for (let i = 0; i < this.spanningTreeChildren.length; i++) {
      if (vertexId === undefined || vertexId != this.spanningTreeChildren[i]) {
        neighbours.push(this.spanningTreeChildren[i]);
      }
    }

    if (this.parentVertexId != null) {
      if (vertexId === undefined || vertexId != this.parentVertexId) {
        neighbours.push(this.parentVertexId);
      }
    }

    return neighbours;
  }
Returns a list of ids of vertices neighbouring this one in the original spanning tree, excluding the ringbond connections.

@param {Number} [vertexId=null] If supplied, the vertex with this id is excluded from the array returned.
@returns {Number[]} An array containing the ids of the neighbouring vertices.