How to use the automerge.getChanges function in automerge

}
        const {
          rev,
          id,
          // rem,
          [mergeField]: automerge,
          [actorField]: actor,
          ...item
        } = i;
        const doc = automerge ? Automerge.load(automerge) : Automerge.init();
        const newDoc = Automerge.change(doc, message, (change: any) => {
          for (var key in item) {
            change[key] = item[key];
          }
        });
        const changes = Automerge.getChanges(doc, newDoc);
        const latestActor = changes.length
          ? changes[changes.length - 1].actor
          : actor;
        delta.push([id, changes, rev]);
        return {
          ...item,
          [actorField]: latestActor,
          id,
          // rem,
          rev,
          [mergeField]: Automerge.save(newDoc)
        };
      });

it(`3a. Bob's edit gets synced to Alice's canvas`, () => {
    const bobChanges3a = Automerge.getChanges(bob2, bob3)
    alice3a = Automerge.applyChanges(alice3, bobChanges3a)
    bob3a = bob3
    assert.deepEqual(alice3a, {
      _objectId: '00000000-0000-0000-0000-000000000000',
      x0y0: 'r',
      x0y1: 'w',
      x1y0: 'w',
      x1y1: 'b'
    })
    assert.deepEqual(alice3a._conflicts, {})
  })

newChange (doc) {
    if (this.previousDoc) {
      const changes = Automerge.getChanges(this.previousDoc, doc)
      changes
        .filter(change => change.actor === this.actor)
        .filter(change => !this.changes[change.seq])
        .forEach(change => {
          const {actor, seq, ...props} = change
          this.changes[change.seq] = props
          this.emit('change', change)
        })
    }
    this.previousDoc = this.watchableDoc.get()
  }

it(`2a. Alice's edit gets synced over to Bob's canvas`, () => {
    const aliceChanges2a = Automerge.getChanges(alice1, alice2)
    bob2a = Automerge.applyChanges(bob2, aliceChanges2a)
    alice2a = alice2
    assert.deepEqual(bob2a, {
      _objectId: '00000000-0000-0000-0000-000000000000',
      x0y0: 'r',
      x0y1: 'w',
      x1y0: 'w',
      x1y1: 'w'
    })
    assert.deepEqual(bob2a._conflicts, {})
  })

ops.forEach(op => {
      const updatedDoc = Automerge.change(lastDoc, doc => applyOperation(doc.doc, op))
      const changes = Automerge.getChanges(lastDoc, updatedDoc);

      lastTransformed = transformer.apply(updatedDoc.doc, changes);
      lastDoc = updatedDoc;
    });

update(doc) {
    this._ensureReady()

    const actorId = this._getActorId(doc)
    const docId = this._actorToId(actorId)
    const pDoc = this.find(docId)
    log('update', docId, actorId)

    const changes = Automerge.getChanges(pDoc, doc)
      .filter(({ actor }) => actor === actorId)

    this._addToMaxRequested(docId, actorId, changes.length)
    this._appendAll(actorId, changes)
    this._set(docId, doc)
    this.emit('document:updated', docId, doc)
    this._handles(docId).forEach(handle => {
      handle._update(doc)
    })

    return doc
  }

update (doc) {
    this._ensureReady()

    const actorId = this.getActorId(doc)
    const docId = this.actorToId(actorId)
    const pDoc = this.find(docId)

    const changes = Automerge.getChanges(pDoc, doc)
      .filter(({actor}) => actor === actorId)

    this._addToMaxRequested(docId, actorId, changes.length)

    this._appendAll(actorId, changes)

    this.pDocs[docId] = doc

    return this.set(doc)
  }

update (doc) {
    this._ensureReady()

    const hex = this.getHex(doc)
    const docId = this.hexToId(hex)
    const pDoc = this.find(docId)

    const changes = Automerge.getChanges(pDoc, doc)
      .filter(({actor}) => actor === hex)

    this._addToMaxRequested(docId, hex, changes.length)

    this._appendAll(hex, changes)

    return this.set(doc)
  }