code: @NonNull
      public Flowable<Changes> observeChangesOfTag(@NonNull String tag, @NonNull BackpressureStrategy backpressureStrategy) {
          checkNotEmpty(tag, "Tag can not be null or empty");
          return observeChangesOfTags(Collections.singleton(tag), backpressureStrategy);
      }
docs: Allows observer changes of required tag.
  <p/>
  Tags are optional meta information that you can attach to Changes object
  to have more fine-grained control over observing changes in the database.
  <p/>
  Notice that {@link StorIOSQLite} knows only about changes
  that happened as a result of Put or Delete Operations executed
  on this instance of {@link StorIOSQLite}.
  <p/>
  Emission may happen on any thread that performed Put or Delete operation,
  so it's recommended to apply {@link Flowable#observeOn(io.reactivex.Scheduler)}
  if you need to receive events on a special thread.
  <p/>
  Notice, that returned {@link Flowable} is "Hot Flowable", it never ends, which means,
  that you should manually dispose from it to prevent memory leak.
  Also, it can cause BackPressure problems.
  
  @param tag tag to monitor.
  @return {@link io.reactivex.Flowable} of {@link Changes} subscribed to changes of required tag.