code: function Duration(str) {
  
    // There must be at least a P
    if(str.length < 1 || str.charAt(0) != 'P') {
      throw new Error('Invalid Duration');
    }
  
    var duration = str.substr(1);
  
    if(duration.length < 1) {
      throw new Error('Invalid Duration');
    }
  
    // 5.3.2 allows for NON normalized durations
    // We assume that if there is a space, it is non-normalized
    if(/\s/.test(duration)) {
      throw new Error('Non normalized durations not implemented');
      //this._parseNonNormalized(duration);
    } else {
      this._parseNormalized(duration);
    }
  
  }
docs: A gedcomX Duration