static guessCodecsSafe(contentType, codecs) {
    const formats = shaka.util.ManifestParserUtils
        .CODEC_REGEXPS_BY_CONTENT_TYPE_.get(contentType);
    for (const format of formats) {
      for (const codec of codecs) {
        if (format.test(codec.trim())) {
          return codec.trim();
        }
      }
    }

    // Text does not require a codec string.
    if (contentType == shaka.util.ManifestParserUtils.ContentType.TEXT) {
      return '';
    }

    return null;
  }
Attempts to guess which codecs from the codecs list belong to a given
content type. Does not assume a single codec is anything special, and does
not throw if it fails to match.

@param {string} contentType
@param {!Array<string>} codecs
@return {?string} or null if no match is found