public function addRule($rule, array $newFormat = array())
{
if (!$rule) {
throw new Exception('Empty rule name');
}
if (array_key_exists($rule, $this->_rules)) {
throw new Exception('Format "' . $rule . '" already exists');
}
$this->_rules[$rule] = array_merge($this->_default, (array) $newFormat);
}