static getVariantStreams(variant) {
    const streams = [];

    if (variant.audio) {
      streams.push(variant.audio);
    }
    if (variant.video) {
      streams.push(variant.video);
    }

    return streams;
  }
Get all non-null streams in the variant as an array.

@param {shaka.extern.Variant} variant
@return {!Array<shaka.extern.Stream>}