public function setProcessorType($processorType)
    {
        if (!in_array($processorType, static::$allowedProcessorTypes))
        {
            throw new RuntimeException("Unknown transaction processor type given: {$processorType}");
        }

        if (!empty($this->processorType))
        {
            throw new RuntimeException('You can set payment transaction processor type only once');
        }

        $this->processorType = $processorType;

        return $this;
    }