code: function (str) {
    var matches = str.match(/([b#]?)([iIvV]+)([mMxoøs]?)/);
    var alteration;
    var numeral;
    var quality;
  
    if (!matches) {
      throw new Error('Invalid Mehegan symbol');
    }
  
    alteration = matches[1];
    numeral = matches[2].toUpperCase();
    quality = matches[3];
  
    if (!quality) quality = inferQuality(numeral);
  
    return new Mehegan(alteration + numeral, quality);
  }
docs: Create a Mehegan symbol given a Mehegan string