getEdgeNormals(edge) {
    let v1 = this.graph.vertices[edge.sourceId].position;
    let v2 = this.graph.vertices[edge.targetId].position; // Get the normalized normals for the edge

    let normals = Vector2.units(v1, v2);
    return normals;
  }
Get the normals of an edge.

@param {Edge} edge An edge.
@returns {Vector2[]} An array containing two vectors, representing the normals.