Why I Can not override \Magento\Paypal\ModelConfig class Either preference or plugin through in magento2?

Question

I want to add some more parameters in _mapWppFieldset().

But I am not able to override this config class in magento2

di.xml

             <?xml version="1.0"?>
             <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
              <preference for="Magento\Paypal\Model\Config" type="Vendor\Paypal\Model\Config" />

Vendor\Paypal\Model\Config.php

                <?php


             namespace Vendor\Paypal\Model;

         use Magento\Payment\Helper\Formatter;


       class Config extends \Magento\Paypal\Model\Config
      {
         protected function _mapWppFieldset($fieldName)
           {

    switch ($fieldName) {
        case 'api_authentication':
        case 'api_username':
        case 'api_password':
        case 'api_signature':
        case 'sales_api_signature':
        case 'sales_api_username':
        case 'sales_api_password':
        case 'payments_api_signature':
         case 'payments_api_username':
        case 'payments_api_password':
        case 'billing_api_signature':
         case 'billing_api_username':
        case 'billing_api_password':
        case 'account_api_signature':
         case 'account_api_username':
        case 'account_api_password':
        case 'sandbox_api_signature':
         case 'sandbox_api_username':
        case 'sandbox_api_password':
        case 'api_cert':
        case 'sandbox_flag':
        case 'use_proxy':
        case 'proxy_host':
        case 'proxy_port':
        case 'button_flavor':
        case 'button_type':
            return "paypal/wpp/{$fieldName}";
        default:
            return null;
        }
    }

  }

Answer 1

Call parent constructor in you new file's constructor

public function __construct(
    \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
    \Magento\Directory\Helper\Data $directoryHelper,
    \Magento\Store\Model\StoreManagerInterface $storeManager,
    \Magento\Payment\Model\Source\CctypeFactory $cctypeFactory,
    \Magento\Paypal\Model\CertFactory $certFactory
) {
    parent::__construct($scopeConfig,$directoryHelper,$storeManager,$cctypeFactory,$certFactory);
}

Hope this will resolve your issue