removeEdge(v, w, name) {
    var e = (arguments.length === 1
      ? edgeObjToId(this._isDirected, arguments[0])
      : edgeArgsToId(this._isDirected, v, w, name));
    var edge = this._edgeObjs[e];
    if (edge) {
      v = edge.v;
      w = edge.w;
      delete this._edgeLabels[e];
      delete this._edgeObjs[e];
      decrementOrRemoveEntry(this._preds[w], v);
      decrementOrRemoveEntry(this._sucs[v], w);
      delete this._in[w][e];
      delete this._out[v][e];
      this._edgeCount--;
    }
    return this;
  }
Removes the specified edge from the graph. No subgraphs are considered.
Complexity: O(1).