_addMissingEdges() {
    const edgesData = this.body.data.edges;
    if (edgesData === undefined || edgesData === null) {
      return; // No edges DataSet yet; can happen on startup
    }

    const edges = this.body.edges;
    const addIds = [];

    edgesData.forEach((edgeData, edgeId) => {
      const edge = edges[edgeId];
      if (edge === undefined) {
        addIds.push(edgeId);
      }
    });

    this.add(addIds, true);
  }
add all edges from dataset that are not in the cached state
@private