code: function maybeMapOverVal(fn, val) {
    var vals = val.split(',');
    if (vals.length > 1) {
      return vals.map(function(v) { return v == '.' ? null : fn(v); });
    }
    return val == '.' ? null : fn(val);
  }
docs: VCF values can be comma-separated lists, so here we want to convert them into lists of the proper type, else return the singleton value of that type. All values are also nullable, signified with a '.', we want to watch out for those as well.