// for debugging

    return Array.from(this.graph.getQuads(null, null, null, null)).map((q: Quad) => [q.subject, q.predicate, q.object, q.graph]);

  }

  applyAndSendPatch(patch: Patch) {

    console.time("applyAndSendPatch");

    if (!this.client) {

      log("not connected-- dropping patch");

      return;

    }

    if (patch.isEmpty()) throw "should not get to this point with empty patch";

    this._applyPatch(patch);

    if (this.client) {

      log("sending patch:\n", patch.dump());

      this.client.sendPatch(patch);

    }

    console.timeEnd("applyAndSendPatch");

  }

  _applyPatch(patch: Patch) {

    // In most cases you want applyAndSendPatch.

    //

    // This is the only method that writes to this.graph!

    log("_applyPatch [1] \n", patch.dump());

    this.cachedFloatValues.clear();

    this.cachedUriValues.clear();

    patch.applyToGraph(this.graph);

    if (false) {

      log("applied patch locally", patch.summary());

    } else {

      log("applied patch locally:\n" + patch.dump());

    }

    this.autoDeps.graphChanged(patch);

  }

  getObjectPatch(s: N3.NamedNode, p: N3.NamedNode, newObject: N3.Quad_Object | null, g: N3.NamedNode): Patch {

    // make a patch which removes existing values for (s,p,*,c) and

    // adds (s,p,newObject,c). Values in other graphs are not affected.

    const existing = this.graph.getQuads(s, p, null, g);

    return new Patch(existing, newObject !== null ? [this.Quad(s, p, newObject, g)] : []);

  }

  patchObject(s: N3.NamedNode, p: N3.NamedNode, newObject: N3.Quad_Object | null, g: N3.NamedNode) {

    this.applyAndSendPatch(this.getObjectPatch(s, p, newObject, g));

  }

  clearObjects(s: N3.NamedNode, p: N3.NamedNode, g: N3.NamedNode) {