docs: function(name, property, value, types) {
    if (!(types instanceof Array)) {
      types = [types];
    }
    if (types.indexOf(typeof value) === -1) {
      debug('%s \'%s\' expected %j got: %j', name, property, types, value);
      throw new Error(name + ' \'' + property + '\' expected one of type(s): \'' +
                      types.join(',') + '\' got type: \'' + typeof value + '\'');
    }
  }