edgeRingCount(edgeId) {
    let edge = this.graph.edges[edgeId];
    let a = this.graph.vertices[edge.sourceId];
    let b = this.graph.vertices[edge.targetId];
    return Math.min(a.value.rings.length, b.value.rings.length);
  }
Returns the number of rings this edge is a part of.

@param {Number} edgeId The id of an edge.
@returns {Number} The number of rings the provided edge is part of.