CatalogProvider::getQuantityFormat

static function getQuantityFormat(array $list): ?int
	{
		/*
		first variant
		'RESERVED_QUANTITY_LIST_BY_STORE' =>
		array (
			20 => basket code
				array (
					'0_0' => shipment index
						array (
							3 => 10.0, store id -> quantity
						),
				),
		),

		second variant
		'RESERVED_QUANTITY_LIST_BY_STORE' =>
		array (
			20 => basket code
				array (
					3 => 10.0, store id -> quantity
				),
		),

		'QUANTITY_LIST_BY_STORE' =>
		array (
			289 => basket code
				array (
					5 => 1.0,  store id => quantity
				),
			290 =>
				array (
					5 => 3.0,
				),
			291 =>
				array (
					5 => 4.0,
				),
			),
		),
		*/

		$basketRow = reset($list);
		if (
			empty($basketRow)
			|| !is_array($basketRow)
		)
		{
			return null;
		}

		$row = reset($basketRow);
		if (is_array($row))
		{
			return self::QUANTITY_FORMAT_SHIPMENT;
		}

		return self::QUANTITY_FORMAT_STORE;
	}