public function buildQuery(array $args = []): string
	{
		$out = array_merge(
			$this->payment->getArgs(), // Arguments of the payment
			$args, // Optional helper arguments
			['signature' => $this->payment->getSignature()] // Signature
		);

		$str = [];
		/** @var string|int $val */
		foreach ($out as $key => $val) {
			$str[] = rawurlencode((string) $key) . '=' . rawurlencode((string) $val);
		}

		return implode('&', $str);
	}