function createSet(var_args) {
  const argLength = arguments.length;
  if (argLength == 1 && Array.isArray(arguments[0])) {
    return createSet.apply(null, arguments[0]);
  }

  const rv = {};
  for (let i = 0; i < argLength; i++) {
    rv[arguments[i]] = true;
  }
  return rv;
}
Creates a new object where the property names come from the arguments but
the value is always set to true
@param {...*} var_args If only one argument is provided and it is an array
    then this is used as the arguments, otherwise the arguments are used as
    the property names.
@return {!Object} The new object.