public function configMethod($class, $method, $rules) {
		foreach ($rules as $param => $rule) {
			if (ctype_upper($param[0])
				&& (!is_string($rule) && !($rule instanceof Closure))
			) {
				throw new InvalidRuleException("Type $param only allowed string or Closure as an extra rule.");
			}
		}
		$this->rules[$class][$method] = $rules;
		return $this;
	}