message: Change client.mergeTree to client._mergeTree
diff: @@ -371,7 +371,7 @@ export class Client {
  */
  public rollback?(op: any, localOpMetadata: unknown) {
  if (op.type === MergeTreeDeltaType.INSERT || op.type === MergeTreeDeltaType.ANNOTATE) {
  - const pendingSegmentGroup = this.mergeTree.pendingSegments?.pop?.();
  + const pendingSegmentGroup = this._mergeTree.pendingSegments?.pop?.();
  if (pendingSegmentGroup === undefined || pendingSegmentGroup !== localOpMetadata
  || (op.type === MergeTreeDeltaType.ANNOTATE && !pendingSegmentGroup.previousProps)) {
  throw new Error("Rollback op doesn't match last edit");
  @@ -385,7 +385,7 @@ export class Client {
  const segWindow = this.getCollabWindow();
  if (op.type === MergeTreeDeltaType.INSERT) {
  const removeOp = createRemoveRangeOp(start, start + segment.cachedLength);
  - this.mergeTree.markRangeRemoved(
  + this._mergeTree.markRangeRemoved(
  start,
  start + segment.cachedLength,
  UniversalSequenceNumber,
  @@ -398,7 +398,7 @@ export class Client {
  const rollbackType = (op.combiningOp && op.combiningOp.name === "rewrite") ?
  PropertiesRollback.Rewrite : PropertiesRollback.Rollback;
  const annotateOp = createAnnotateRangeOp(start, start + segment.cachedLength, props, undefined);
  - this.mergeTree.annotateRange(
  + this._mergeTree.annotateRange(
  start,
  start + segment.cachedLength,
  props,
  