How to use the howler.Howler._volume function in howler

export function getSaveData() {
  const globalMuted = Howler._muted;
  const globalVolume = Howler._volume;

  const channels = Object.keys(Pool);
  const channelData = [];

  for (const channel of channels) {
    const sound = Pool[channel];
    const channelVolume = ChannelVolume[channel] || 1.0;

    let pos = sound.seek();

    if (typeof pos !== 'number') {
      pos = 0;
    }

    channelData.push({
      channel,