Assert\Assertion::string PHP Method

    public static function string($value, $message = null, $propertyPath = null)
    {
        if (!is_string($value)) {
            $message = sprintf($message ?: 'Value "%s" expected to be string, type %s given.', static::stringify($value), gettype($value));
            throw static::createException($value, $message, static::INVALID_STRING, $propertyPath);
        }
        return true;
    }

 private function setPath($path)
 {
     Assertion::string($path);
     Assertion::regex($path, '|(?mi-Us)^(/[a-zA-Z][a-zA-Z0-9_-]*)+(/@[a-zA-Z][a-zA-Z0-9_-]*)?$|');
     $this->path = $path;
     return $this;
 }