getEdgesForSet(tiddlers, toWL, typeWL) {

    const edges = utils.makeHashMap();
    for (let i = tiddlers.length; i--;) {
      Object.assign(edges, this.getEdges(tiddlers[i], toWL, typeWL));
    }

    return edges;

  }
The method will return all outgoing edges for a subset of tiddlers.

@param {Array<Tiddler>} tiddlers - The set of tiddlers to consider.
@param toWL
@param typeWL
@return {Hashmap<Id, Edge>} An edge collection.