async startPolling(pollOptions = {}) {
        if (this.stopped) {
            this.stopped = false;
        }
        while (!this.isStopped() && !this.isDone()) {
            await this.poll(pollOptions);
            await this.delay();
        }
    }
fireProgress calls the functions passed in via onProgress the method of the poller.

It loops over all of the callbacks received from onProgress, and executes them, sending them
the current operation state.

@param state - The current operation state.